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. 

Chronic Inflammation And Depression

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Inflammation is the body’s natural response to infection or injury. It’s an important response in the acute setting but chronic inflammation can contribute to the development of diseases such as heart disease and even depression. Most psychiatrists now recognize that inflammation plays a role in depressive disorders, although it’s not an inflammatory disease. Much of the research on inflammation and depression is ongoing and will develop over time. 

Risk Factors for Inflammation

·         Childhood trauma

·         High stress levels (work, school)

·         Depression that is resistant to treatment

·         Severe anxiety

·         Obesity BMI> 30

·         Medical illness

·         Recent injury or surgery

What are some nonpharmacological things we can do to reduce inflammation and thus the risk of disease?

Complementary and alternative therapies

Lifestyle: Exercise, Healthy diet, Mindfulness practice, CBT all have anti-inflammatory effects.

N-acetylcysteine studies with 2000 mg/day improved anxiety and depressive symptoms

L-methyl folate: L-methyl folate 15 mg/day as augmentation to antidepressants

Omega-3: 1000 mg/day of omega-3 fatty acids with DHA to EPA ratio > 60% improved depressive symptoms

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