What Can We Do to Help Prevent Alzheimer’s disease (AD)


The other day I had a conversation with a friend, and the topic of Alzheimer’s disease (AD) came up. My friend’s opinion was basically why would I want to know I have a disease that results in steady decline in function, and lacks any disease modifying treatments? This is in large part true, there have been multiple clinical trials of both symptomatic and disease modifying drugs that failed to produce adequate results. However, this is a very limitted view and neglects the benefits of focusing on modifiable risk factors and primary prevention. We know approximately 1/3rd of AD cases are due to modifiable risk factors, and the implementation of lifestyle modification early may prevent or delay the onset of AD. 

Modifiable Risk Factors

Common modifiable risk factors for AD include hypertension, hyperlipidemia, diabetes, obesity and smoking. Management of these risk factors as early as possible may offer a preventative approach for AD. Equally important are lifestyle modifications such as physical exercise, diet, mediation/mindfulness, and social activity.

Physical Activity

Physical inactivity has a significant influence on the development of AD. Twenty-one percent of AD cases are attributable to physical inactivity. There is a significant number of studies in the literature that indicate physical activity is neuroprotective. We know one of the areas in the brain affected by physical activity is the hippocampus which is involved in memory. Exercise leads to increased neurogenesis and neuroplasticity in the hippocampus. Other benefits of exercise on the brain include increased blood flow, modulation of inflammatory markers, and increased brain-derived neurotrophic factor (BDNF). The exact definition of adequate exercise varies in the literature. Any activity that is sufficient to increase heart rate and can be sustained for 30-60 minutes is my definition. A basic example would be brisk walking for 30-60 minutes. Physical activity two times a week beginning in middle age is associated with reduced risk of AD. Aerobic exercise is associated with additional cognitive benefits including improved processing speed, attention, and memory in adults with mild cognitive impairment. This recommendation is especially important for ApoE4 carriers, as exercise is associated with reduced amyloid deposits. 

Physical activity should be a recommendation for all patients without major health concerns preventing physical activity. The earlier in life a patient begins an exercise routine the better. Some of these studies have looked specifically at starting exercise routines in middle age, but there is no reason to wait. The physical and cognitive benefits of exercise are beneficial regardless of age. It’s much easier to begin training when you are young and healthy. If you build healthy lifestyle habits earlier in life, they are likely to last as you age. Guidelines for regular exercise can be found on the American Heart Association or American College of Sports Medicine websites. 


Meditation or mindfulness is a topic that is beginning to get more attention in the medical literature. Chronic stress is believed to effect brain structures involved in memory and may contribute to AD. Psychological stress increases oxidative stress and telomere shortening which could contribute to the neuronal loss seen in AD. Meditation has emerged as a possible way to reduce the stress associated with daily life. The techniques of mindfulness involve directing one’s attention to the present moment to reduce the stress associated with constant thinking and worrying. Randomized controlled trials (RCTs) have shown significant improvements in overall well-being and attention. Improved executive function and reduced inflammatory processes implicated in AD. Additional research and larger RCTs are needed to improve the evidence base. Given the data we currently have there is no reason to not begin mindfulness practices. The techniques are relatively simple and can be learned from a variety of sources. If you are looking for low cost options for learning mindfulness, YouTube has a variety of guided mediations available. I personally like Headspace for beginners because it provides a solid foundation, has a variety of meditation courses, and allows you to track your progress. There is a fee for access to all the courses, but the first 10 sessions are free. Whichever route you choose, spending 10-15 minutes per day practicing mindfulness will lead to a happier and healthier brain. 


A great deal of research has been conducted over the last several years on the role of diet with respect to cognition. People with high calorie diets, specifically those high in fat are at higher risk for AD. Traditional western diets high in processed carbohydrates, simple sugars, and saturated fatty acids can impact the hippocampus and memory. When Japan transitioned to western diet the incidence of AD increased. Lower calorie diets with lower saturated fat content are linked to lower oxidative stress, decreased Beta amyloid burden, and decreased inflammation. One diet with proven benefits for preventing AD is the Mediterranean diet. This diet is rich in fruits, vegetables, whole grains, olive oil, and fish. There is moderate intake of low-fat dairy products and low intake of red meat, saturated fats, and sugar. Most of the data supporting the reduce risk of AD with this diet comes from epidemiological studies. Studies have shown combining this diet with exercise further reduces the risk of AD. The Mediterranean diet is associated with better cognitive function and reduced cognitive decline. This is one specific example, but the basic principles can be applied without the need to adhere to one specific named diet. 

Some specific foods you may want to add to your diet to prevent AD include fresh berries which have the highest amounts of antioxidants among the fruits. They are also low in calories and work well in diets where weight loss is a goal. Green leafy vegetables and tomatoes have the highest nutritional value when it comes to brain health amongst the vegetables. Foods high in omega-3 fatty acids are considered to be helpful in supporting brain function. The omega-3 fatty acid most important in brain function is docosahexaenoic acid (DHA), which is mostly found in fish. The anti-inflammatory and antioxidant properties of DHA are thought to be responsible for its role in preventing AD. Patients with diagnosed AD are known to have low levels of DHA. Omega-3 fatty acids recommendations from the American Heart association for adults is to eat fish rich in omega-3s two or more times per week. If using a supplement 1-3 grams per day is an adequate dose. Over 3 grams per day, you should consult with your doctor before moving above 3 grams per day. 

Finally, curcumin which is derived from turmeric has anti-inflammatory, antioxidant, and anti-amyloid properties. There is low bioavailability of the curcumin lead to mixed results in the initial trials. A new more bioavailable form called Theracumin demonstrated positive results in a randomized double-blind placebo-controlled study on memory, attention, and amyloid plaques in older adults without dementia. 


While there is no guarantee that lifestyle modification alone will prevent AD, there are some promising studies indicating it plays a role in the development of this disorder. Most of these interventions are things patients can implement in their lives immediately. They will not only improve cognitive function and lower the risk of developing AD, but it will improve and potential reverse other diseases of lifestyle. 

Complementary Alternative Medicine (CAM) in Psychiatry

This is one of the most popular topics patients ask about. Often psychiatry gets a bad reputation for prescribing medication without addressing lifestyle and “natural” options for the treatment of psychiatric illness.

A 2007 National Health Interview Survey (NHIS) reported 4 out of 10 American adults and 1 out of 9 children used CAM. The most commonly cited reasons for using CAM are depression, insomnia, anxiety, and chronic pain. Typically, integrative care involves the use of traditional medical therapy with appropriate evidence-based CAM. This is not always the case, and often times you will find many people who are not licensed medical doctors offering advice on CAM. What I hope to accomplish in this post is to introduce some of the CAM options that are evidence based for depression.

While the use of CAM is widespread, randomized controlled trials for specific CAM interventions have issues with their study design. They are usually conducted for short durations, and have a small number of participants. Despite these limitations, many CAM research studies report positive benefits for depression. Likewise finding high quality products with appropriate dose of active ingredient can also be a challenge. There are many companies and not all of them are reputable. 

It’s unlikely that CAM will be enough to treat severe cases of major depressive disorder alone. For mild to moderate cases of depression, it may be effective based on the evidence detailed below.

Below are the options I would consider CAM for primary treatment of depression. In the next post I will talk about adjunctive treatment for people who have had response to antidepressants but not remission of symptoms.

Hypericum Perforatum (St. John’s Wort) 

St. John’s Wort (SJW) is a medical herb with antidepressant activity. The exact mechanism by which this herb improves mood is not fully understood. SJW is known to inhibit monoamine reuptake, and down regulate monoamine receptors in the brain. In 2005 Linde et.al conducted a meta-analysis of 37 randomized double-blind placebo-controlled trials (RCT) which demonstrated superiority of SJW to placebo. It’s important to note SJW was equivalent to antidepressant treatment for mild cases and inferior for severe depression. In 2017 Ng QX et al. conducted a meta-analysis which found a similar result. They looked at 27 clinical trials and a total of 3808 patients, comparing the use of SJW with SSRIs for the treatment of depression. They concluded that for mild to moderate depression, SJW had comparable efficacy and safety when compared to SSRIs.

How does SJW stack up against traditional SSRIs? Fava et al. conducted a randomized double-blind trial of SJW, fluoxetine and placebo for major depressive disorder. SJW was significantly more effective than fluoxetine and showed a trend toward superiority over placebo. Sarris et al. analyzed date from a 26-week RCT that studied SJW vs. Sertraline and placebo for major depressive disorder. The comparison between all treatments was not significant. Both SJW and sertraline were therapeutically effective, but they could not say one was superior to the other. 

Although SJW is effective for the treatment of depression, it’s not my favorite choice. SJW is a known inducer of the cytochrome P450 enzymes. SJW can increase clearance of medications including antiretrovirals, oral contraceptives, benzodiazepines, digoxin, and phenobarbital. When SJW is combined with other antidepressant medication there is increased risk of serotonin syndrome. 

S-Adenosyl-Methionine (SAMe)

SAMe is an amino acid that is distributed widely throughout the brain and is the major methyl donor required for the synthesis of monoamine neurotransmitters. It’s available in the United States over the counter. Studies indicate that SAMe levels may be reduced in patients with MDD.

Several reviews of the literature on SAMe and depression have been conducted. Most of the reviews conclude that SAMe is generally effective for the treatment of depression. However, more carefully designed higher quality studies need to be conducted. A meta-analysis that looked at 28 studies concluded that SAMe was superior to placebo for the treatment of depression, and it was found to be statistically significant. Again, this study did not find a difference between SAMe and traditional antidepressant treatment. Another review of 11 studies concluded that SAMe resulted in a reduction in depressive symptoms and was superior to placebo. One study showed benefits of SAMe as an adjunctive therapy to SSRIs in patients who were non-responders.

SAMe does have some associated side effects including mild gastrointestinal (GI) problems and insomnia. There is risk of inducing a manic episode in patients with bipolar disorder, and SAMe should be avoided in this population. Patients taking medication for Parkinson’s disease may have reduced efficacy of the medication when taken in conjunction with SAMe. Thus, we should avoid SAMe in this population as well. 


  1. Linde K, Berner MM, Kriston L. St John’s wort for major depression. Cochrane Database Syst Rev. 2008;2008(4):CD000448. Published 2008 Oct 8. doi:10.1002/14651858.CD000448.pub3
  2. Ng QX, Venkatanarayanan N, Ho CY. Clinical use of Hypericum perforatum (St John’s wort) in depression: A meta-analysis. J Affect Disord. 2017;210:211-221. doi:10.1016/j.jad.2016.12.048
  3. Fava M, Alpert J, Nierenberg AA, et al. A Double-blind, randomized trial of St John’s wort, fluoxetine, and placebo in major depressive disorder. J Clin Psychopharmacol. 2005;25(5):441-447. doi:10.1097/01.jcp.0000178416.60426.29
  4. Sarris J, Fava M, Schweitzer I, Mischoulon D. St John’s wort (Hypericum perforatum) versus sertraline and placebo in major depressive disorder: continuation data from a 26-week RCT. Pharmacopsychiatry. 2012;45(7):275-278. doi:10.1055/s-0032-1306348
  5. Galizia I, Oldani L, Macritchie K, et al. S-adenosyl methionine (SAMe) for depression in adults. Cochrane Database Syst Rev. 2016;10(10):CD011286. Published 2016 Oct 10. doi:10.1002/14651858.CD011286.pub2
  6. Sharma A, Gerbarg P, Bottiglieri T, et al. S-Adenosylmethionine (SAMe) for Neuropsychiatric Disorders: A Clinician-Oriented Review of Research. J Clin Psychiatry. 2017;78(6):e656-e667. doi:10.4088/JCP.16r11113

Depression Etiology: Brain-Derived Neurotrophic Factor (BDNF)

Brain-Derived Neurotrophic Factor (BDNF) is a substance in the brain that promotes neuronal growth. It’s also involved in neuroplasticity in the developing brain. There is increasing interest in the role of BDNF in depression for several reasons.

We know that various brain structures are decreased in size in patients with major depressive disorder. Specific areas include the anterior cingulate, prefrontal cortex, and amygdala all of which are implicated in depression. Decreased serum levels of BDNF have been found in patients with depression and may be in part responsible for these changes.

Mutations to the BDNF gene have been associated with major depressive disorder (MDD). Antidepressant medications can increase BDNF, and in part may explain the effects of these medications.

Depression etiology: Hypothalamic-Pituitary-Thyroid Axis Dysregulation

We are almost done building up the discussion about potential causes or contributing factors for depression. This post will focus on the role of the thyroid. 

Evidence Supporting Thyroid Dysfunction In Depression

It’s well established that thyroid dysfunction is associated with depression. Some evidence to support the theory that thyroid function is linked to depression includes a significant number of depressed patients who are hospitalized have a diagnosis of hypothyroidism (around 10%), thyroiditis is more common in mood disorders, patients with rapid cycling bipolar disorder are more likely to have hypothyroidism, and triiodothyronine (T3) is used as a augmentation strategy for difficult to treat depression.

One of the things we need to do prior to making a diagnosis of depression is to rule out potential medical causes. Looking for the following signs and symptoms, as well as laboratory testing can be helpful in assessing thyroid function.

The following symptoms are common in Hypothyroidism

  • Fatigue 
  • Cold intolerance 
  • Impaired memory and concentration 
  • Constipation 
  • Weight gain 
  • Shortness of breath 
  • Hoarse voice 

The following Signs may be present

  • Dry skin 
  • Cool extremities 
  • Hair loss 
  • Low pulse rate 
  • Delayed deep tendon reflexes 
  • Carpal tunnel syndrome 

Lab Testing and Physical Exam

Lab testing for TSH levels is the best initial test. It may need to be repeated in a few weeks to ensure the levels are truly elevated. Another way to help make the diagnosis is order a free T4 blood level to determine if this is subclinical hypothyroidism. If a lump or a mass is felt on thyroid during physical exam diagnostic imaging may be required. The presence of antibodies against thyroid peroxidase (Anti-TPO) provides evidence to support autoimmune thyroiditis as the cause of hypothyroidism.

Treatment For Hypothyroidism

Treatment includes hormone replacement. The long-acting form of thyroxine is called levothyroxine. A psychiatrist will likely recommend the primary care provider manage the diagnosis and treatment. 

Final Comments:

The need to treat depression while the work-up for hypothyroidism is occurring will depend on the clinical picture. Generally, I would prefer to wait until the hypothyroidism is treated adequately, but this is not always possible. 

Depression etiology: Hypothalamic-Pituitary-Adrenal Axis Dysregulation

Elevated cortisol levels over 24 hours have been observed in patients with MDD. Cortisol is a steroid hormone in the glucocorticoid class of hormones. It’s released in response to stress and low-blood glucose. It functions to increase blood sugar, suppresses the immune response, and aids in the metabolism of fat, protein, and carbohydrates. 

In studies a test called the dexamethasone suppression test (DST) has been used to assess cortisol release in depressed patients. Nelson and Davis used this test in patients with depression. They found that 41% of those with MDD with melancholia and 64% of those with MDD with psychotic features either had decreased suppression or were non-suppressors of serum cortisol. They determined that the utility of this test in routine clinical practice is limitted due to low sensitivity and specificity. 

There is a theory that may explain HPA axis dysregulation in depressed patients. Patients who are depressed, may have a dysfunction in the ability of cortisol-glucocorticoid receptor complex to enter the cell. This will disrupt the negative feedback mechanism which tells the body to stop producing cortisol. The result is increased cortisol levels because there is nothing indicating to the body enough cortisol has been produced. 

Elevated cortisol levels appear to be dependent on the current state of the person. If the person is depressed, levels will be elevated. Once the depressive episode has resolved or the person has been effectively treated with antidepressants the HPA axis appears to normalize. 

Inflammation and Depression Revisited

What is Inflammation?

It can be defined as the body’s natural response to infection or injury. Inflammation can be a good thing and is essential for survival. We also know that chronic inflammation is bad. It’s known to contribute to heart disease, cancer, and neurodegenerative disorders. 

What can we say about depression and inflammation?

Some patients with depression have elevated inflammatory markers. In cardiology, C-reactive protein (CRP) is used as a marker to help predict the risk of cardiovascular disease. Obesity is known to be correlated with inflammation and can result in elevated CRP. The standard American diet contributes to both inflammation and obesity. CRP has also been used in psychiatry, but it’s less clear how to use this to predict risk or severity of depression.

Evidence for the treatment of patients with depression and inflammation

The current recommendation to determine if significant inflammation is present, is to order a high-sensitivity CRP test. The exact cutoff value to indicate significant inflammation is not clear. Somewhere between 1 mg/L and 3 mg/L is a reasonable reference range. We can look to the literature to guide us. There are a few randomized controlled trials available. One such trail in the American Journal of Psychiatry compared escitalopram (Lexapro) to nortriptyline in 241 patients. Patients with high CRP > 3 mg/L did better on Nortriptyline and patients with low CRP 1 mg/L did better on escitalopram (GENDEP Trial). Another trial looked at the use of bupropion (Wellbutrin) as augmentation for 106 patients with major depression currently on escitalopram. Bupropion improved depression for those with a CRP > 1 mg/L (CO-MED Trial). A common factor is both nortriptyline and bupropion have an effect on dopamine. The precise reason that increased dopamine levels seems to improve depression in patients with inflammation is unclear. However, this provides some evidence and can inform treatment decisions.

Pharmacotherapy for patients with depression and inflammation

  1. Nortriptyline: If the patient has a CRP >3 there is evidence to support the use over SSRIs specifically escitalopram from GENDEP Trial
  2. Bupropion: For patients with CRP >1 or obesity augmentation with bupropion may improve depressive symptoms. 
  3. Lurasidone: commonly used to treat bipolar depression, has some evidence to support its use when CRP > 2 
  4. Pramipexole: has some evidence to support its use in animal models, and off label use in treatment resistant depression

Final Notes

I do not believe all of these new insights into inflammation and depression are ready to be considered standard of care in psychiatry. For patients struggling with obesity, are treatment resistant, or had a poor response to initial antidepressant treatment may benefit from ordering a CRP level and letting it help guide medications choices. Like most things in science more research is required, but inflammation remains an interesting target for depression treatment. 

What to Expect When You Visit the Psychiatrist: Part One

The initial psychiatric interview is the beginning of an important relationship. Many things will be determined in the first encounter by both the patient and the psychiatrist. At times this can feel overwhelming. A large amount of information must be gathered, processed, and incorporated into a cohesive treatment plan. This series of posts is designed to shed some light on the process, and reduce the anxiety associated with undergoing a psychiatric evaluation. 

The interview consists of five key parts: (1) introduction, (2) opening, (3) the body, (4) closing, and (5) termination. A good psychiatrist will blend these sections into each other, so it feels more like a conversation than a formally structured interview. 

Part 1: The Introduction

This is an important phase and begins as soon as the psychiatrist and patient see each other. The primary goal is to engage the patient and get them comfortable before asking sensitive questions. Like other first encounters the patient will form an impression of the psychiatrist which will shape the rest of the interview and treatment process. 

One way to ensure patient comfort is to address anything in the office setting that can be altered prior to starting the evaluation. For example, closing a shade due to light from the window shining directly on the patient’s seat. Another example would be offering a drink of water or tea before starting. A simple gesture of kindness goes a long way in helping the patient feel comfortable in the setting. 

The psychiatrist should then proceed with a formal introduction and offer a few details about himself or herself. One fear many patients have is a friend or family member finding out that they are under the care of a psychiatrist. It’s always a good idea to clarify and ensure confidentiality. Confidentiality is strictly maintained with the exception two primary scenarios (may vary by state). If a patient informs the psychiatrist of a plan to kill themselves or someone else, there is a duty to warn and protect the patient. 

Once these parts are complete a brief description of how the interview process works is in order. 

An example of this interaction may occur as follows:

The purpose of today’s interview is to learn about your concerns and the types of stressors you are dealing with. As the interview progresses, I will get a better idea of the primary concerns. We will then transition to some background questions about your family, medical health, schooling, and any previous psychiatric care you received. At the end of the discussion we can work together on a treatment plan. This process will take approximately one hour. Do you have any questions before we get started?

We want to convey two things to the patient, (1) a sense of understanding about the interview process to reduce fear, and (2) altering the patient to the fact that many questions will be asked, and it will take a fair amount of time. 

The structure of the introduction is not set in stone and may be modified. It should take around five to seven minutes to complete. 

In the next post we will tackle the opening of the interview process. 


Diagnosis Depression: Sleep Dysregulation

One of the most common symptoms found in multiple psychiatric disorders is sleep disturbance. In fact, sleep disturbance is one of the criteria for the diagnosis of major depression. This post will offer an explanation of some of the changes observed in the sleep patterns of depressed patients.

Much of this information comes from sleep studies in patients who have a diagnosis of major depressive disorder. Without getting too technical there are two primary types of sleep, non-rapid eye movement sleep (NREM) and rapid eye movement sleep (REM). The NREM sleep can be broken down further but for the sake of simplicity we will consider these two categories. 

What we notice in sleep studies of patients who suffer from major depression is a much faster onset of REM sleep. The body usually cycles through these stages 4-6 times throughout the night, averaging 90 minutes in each stage. As the night progress NREM sleep decreases and REM sleep increases. A person with normal sleep architecture will enter REM after 90 minutes, in patients with depression this time period is shorter and can be observed on the sleep study results.

Other changes include decrease NREM sleep which can be thought of as restorative sleep. Increased REM density reduced total sleep time, and decreased sleep continuity are also present. 

Any single change in sleep architecture is not diagnostic of major depression. However, taken together decreased onset to REM, increased REM density, and decrease sleep efficiency can separate patients with major depression from a control group. 

Given all of this information, routine sleep studies are not diagnostic for major depression and are not routinely ordered unless you suspect another sleep disorder. 

Hopefully this provides a basis for why questions about sleep in depressed patients are important. The sleep changes also provide some objective evidence of altered sleeping patterns in patients with depression. 

The Biochemical Theory of Depression


How many times in a casual conversation about depression have you heard someone use the term chemical imbalance? Have you ever asked yourself where that idea comes from?  

This is the way many people think about depression, as a “chemical imbalance.” It all seems so intuitive. If there is a chemical missing from the body, you should theoretically be able to replace that chemical and solve the problem. However, the question remains, how did we come up with this idea in first place? This post will attempt to explain how the biological basis of depression was formed. If you can understand these concepts, it lays the groundwork for understanding how many medications for depression work.

Biogenic Amine Hypothesis

The current prevailing biochemical theory of depression is called the biogenic amine hypothesis. The name is a little complex so we can use serotonin as our example. It’s the neurotransmitter most commonly associated with depression and it happens to be a biogenic amine. This was the first attempt to explain the biological basis for depression and evolved from observations that certain medication had either a positive or negative effect on mood. 

Mood & Neurotransmitters 

One early observation of medication effecting mood was with the drug iproniazid which was designed to treat tuberculosis. The researchers observed that it wasn’t very effective for tuberculosis, but it did enhance the mood of some patients. The researchers hypothesized that it was the medications ability to inhibit metabolism of norepinephrine, serotonin and dopamine thus increasing these levels in the brain that provided the antidepressant effect. Iproniazid is what you would call a monoamine oxidase inhibitor (MAOI) which is an older class of medication for depression. It’s rarely used today due to the side effect profile, but hopeful this illustrates the concept. 

Further support for the theory comes from animal studies with the antidepressant medications in the tricyclic antidepressant (TCA) family. These medications block the reuptake of serotonin and norepinephrine thus increasing the levels in the brain. This illustrates the same concept as the (MAOI) discussed above, increase serotonin and norepinephrine in the brain and mood improves. 

Problems with the Theory

One issue with the theory was these medications begin blocking reuptake within minutes, but the antidepressant effects take several weeks to occur. More recent research has shown that these medications down regulate certain receptors, but even with this it’s unlikely to fully explain the antidepressant effects of the medication. While this remains the prevailing theory, it’s clear that there is more to learn about the way these neurotransmitters interact with receptors. Some of the newer medications for depression do not function in the manner as those listed above, but still provide antidepressant effects.

Final Points

  • The biogenic amine hypothesis, is just that it’s a hypothesis about how these medications work on depression 
  • Most of the early evidence was observational, and with medications initially designed to address other disorders. 
  • While the biogenic amine hypothesis is incomplete and does not fully explain depression, It provides a useful framework for future study and drug design 

Is Depression A Genetic Disorder?


This is a common and difficult question I get asked. Like everything in psychiatry, the answer is not clear.

When people think about genetic disorders, they tend to think about classic genetic diseases. Some examples would be sickle cell anemia or cystic fibrosis. There is a clear pattern of inheritance with a single gene involved in these diseases

The human genome project set out to sequence the entire human genome. While it accomplished the goal it did not offer the personalized medicine and targeted interventions initially promised. What it did reveal was a more complicated interplay of genetics and environmental factors. Depression is a multifactorial disease and does not have a single gene involved in the disorder. 

Let’s look at some the evidence supporting the genetic influence on the development of depression.

What Can Family studies tell us ?

The first place to look for a genetic link is family studies. This is one reason we obtain a family history in a psychiatric interview.

MDD is common in families. It’s found 2 to 3 times more often in first-degree biological relatives (e.g. mother or father) of individuals with the disorder than the general population. It’s important to note that the influence of genetics on the development of depression depends on the percent of the genome shared by the individuals. For example, first-degree relatives who share 50% of their genome will have a much greater influence than a second-degree relative who shares 25% of the genome.

What can twin studies tell us ?

The second area of evidence that supports the influence of genetics on depression comes from twin studies.

From the data we know for monozygotic twins (identical twins), there is a 50% chance that one twin will develop the trait (e.g. depression) if the other twin has depression. This number decreases to 20% for fraternal twins who only share 50% of their genome. One flaw in many of these studies is the twins were often raised together in the same environment. There is clearly something to be said for the influence of environment. Some researchers believe twins will influence each other’s behavior when raised together. Identical twins have been known to be treated more similar by their parents than fraternal twins. Taken at face value, when a twin with 100% of the same genetics (identical twins) develops depression the other twin is more likely to also develop depression. Keep in mind, they do not always develop depression even if they share 100% of the genome. 

What do adoption studies add?

Adoption studies make an attempt to differentiate the influence of genetics from environmental factors. These studies examine differences in rates of illness among biological relatives as opposed to adoptive relatives. The studies show higher rates of illness among biological parents rather than adoptive parents. This provides some additional evidence to support a genetic influence. 


There is clearly a genetic component to depression. However, it’s a complicated process that involves multiple genes interacting with the environment. This makes identifying a single causal gene difficult and likely impossible. There are people biologically predisposed to developing depression, but not everyone with biological predisposition will go on to develop depression. 

If you found this helpful please like, comment and share your thoughts for future posts on genetics.

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