FTC Doesn't List "Weight Gain" As Side Effect Of Common Antidepressants

The Federal Drug Administration (USA) lists the common side effects of SSRI antidepressants as,

• Nausea
• Tremor (shaking)
• Nervousness
• Problems sleeping
• Sexual problems
• Sweating
• Agitation
• Feeling tired

The same page also lists common side effects of SNRI's and tricyclic antidepressants.

Weight gain isn't listed as a side effect of any of the SSRI, SNRI or tricyclic antidepressants.

Interestingly, on that page, it's only mentioned for the "atypical antidepressant", Remeron (mirtazapine).

New evidence suggests that "weight gain" should be listed as a side effect for common antidepressants.

I've heard, anecdotally, from someone who tried antidepressants but couldn't stick with them because she gained weight each time. You can also find examples of people mentioning "weight gain" as a side effect with social media searches. I was researching for something else when I found this one on Reddit...

Obviously, it's not a good idea to rely on anecdotal evidence for decision making, but now a large study has been published that backs up the anecdotal evidence.

New Study Suggests Common Antidepressants Do Cause Weight Gain

Published this month in the Journal of Annals of Internal Medicine, a new study looked at prescription data from 183,118 adults aged 18 to 80 to see which of the common antidepressants cause weight gain.

Performed by investigators from the Harvard Pilgrim Health Care Institute, the study was retrospective, so did data-mining using the US-based PCORnet, (National Patient-Centered Clinical Research Network) database.

This wasn't a randomized controlled trial, so there were no controls, and therefore it's not possible to say for certain that the weight gain was due to the antidepressants. However, the fact that every antidepressant showed this characteristic is indicative of it being inherent to these drugs, perhaps by increasing appetite.

The study looked at 8 different antidepressants, with sertraline (Zoloft) serving as a baseline, probably because it's the most commonly prescribed antidepressant. The other antidepressants were:

• Citalopram (Celexa)
• Escitalopram (Lexapro)
• Fluoxetine (Prozac)
• Paroxetine (Paxil)
• Bupropion (Wellbutrin)
• Duloxetine (Cymbalta)
• Venlafaxine (Effexor)

Participants hadn't taken antidepressants in the 6 months prior to the start of the study.

All of the people taking antidepressants showed a weight gain, on average, over the 2 year period, with escitalopram, paroxetine, and duloxetine gaining the most (up to 1.8kg, 4 pounds, over two years). Duloxetine takers only saw a weight gain of about 1kg (2 pounds) over the two years.

Are There Different Sensitivities To This Side Effect?

It's possible that some people are more sensitive to this weight gain side-effect of anti-depressants. As with a lot of side effects, some people experience them while other don't. If that's the case with weight gain, some people may gain considerable weight while others are unaffected by this side effect. The average may come out at a few extra pounds in weight, but that may be a distortion of averaging affected and unaffected people. 

The Problem Of Weight Gain As An Antidepressant Side Effect

The major problem with weight gain as a side effect of taking antidepressants is that it may make it more likely that people will stop taking their medication. People stop taking antidepressants for many reasons. Indeed, in this study, the number of people taking their antidepressant fell to roughly a third after six months, a fifth after twelve months and just a twentieth after two years!

While it's possible that people are coming off antidepressants because they're "cured" of depression, it's also possible that side effects and lack of drug effectiveness may cause people to cease taking them.

If there's not a medical reason to choose one antidepressant over another, the weight-gain side effects of these antidepressants could play a role in deciding which to prescribe at the outset. By doing so, the prescribing doctor could help ensure the patient continued with the medication.

People Who Should Avoid Antidepressants When Weight Gain Is A Side Effect

Example 1: a diabetic patient, wanting close control over their weight, may be more suited to an antidepressant less likely to cause weight gain.

Example 2: someone with a history of eating disorders and/or body dysmorphia may be strongly averse to weight gain and may stop taking the antidepressant if weight gain happens. In this situation, weight gain may actually accentuate depression, the exact opposite of the desired outcome. Care should be taken to suggest an anti-depressant with minimal weight-gain as a side effect in this situation, or look at other treatments initially.

Which Anti-Depressants Were "Best" And "Worst"?

In this study, people taking the atypical antidepressant, bupropion (Wellbutrin, Zyban), were 15-20% less likely to gain a "clinically significant" amount of weight, defined as 5% or more of their initial bodyweight, relative to sertraline, in the first six months.

On the other hand, those who took escitalopram or paroxetine had a 15% higher chance of gaining 5% or more of their body weight, relative to sertraline. Interestingly, all three are SSRI's, so even within a class of antidepressants, there are variations in the weight gain side effect.

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Paper cited: Medication-Induced Weight Change Across Common Antidepressant Treatments