Antidepressants are commonly prescribed, FDA-approved medications used to treat depression, anxiety, and other related mental health disorders.
Though antidepressants can be effective at treating these conditions, they can also cause a range of side effects, including weight loss.
In this article, I’ll describe what antidepressants are, their effect on weight, and which antidepressants are known to cause weight gain or weight loss.
Finally, I’ll explain whether antidepressants have ever been prescribed specifically for weight loss and whether you can safely prevent weight loss due to antidepressants.
What are Antidepressants?
Thankfully, both anxiety and depression can be treated with antidepressants, cognitive behavioral therapy, or a combination of treatment modalities.
Antidepressants are a popular prescription treatment for several mental health conditions, including:
- Major depressive disorder (MDD)
- Obsessive-compulsive disorder (OCD)
- Panic disorder
- Premenstrual dysphoric disorder (PMDD)
- Posttraumatic stress disorder (PTSD)
- Social anxiety disorder (SAD)
Most antidepressants work by affecting chemicals in the brain called neurotransmitters, including serotonin, norepinephrine, and dopamine.
There are five main classes of antidepressants which affect these neurotransmitters in different ways:
- Selective serotonin reuptake inhibitors (SSRIs): SSRIs are often the first-line treatment prescribed by doctors for depression and anxiety. SSRI medications generally cause fewer side effects and are less likely to cause problems at higher therapeutic doses than other types of antidepressants. As suggested by their name, SSRIs work by increasing the activity of the chemical serotonin in the brain. Examples of SSRI medications include sertraline (Zoloft), fluoxetine (Prozac), paroxetine (Paxil), fluvoxamine (Luvox), citalopram (Celexa), escitalopram (Lexapro) and vilazodone (Viibryd).
- Serotonin and norepinephrine reuptake inhibitors (SNRIs): SNRIs work by blocking the reabsorption of the neurotransmitters serotonin and norepinephrine in the brain. Examples of SNRI medications are duloxetine (Cymbalta), venlafaxine (Effexor XR), desvenlafaxine (Pristiq), and levomilnacipran (Fetzima).
- Tricyclic antidepressants: Tricyclic antidepressants can cause more side effects than SSRIs or SNRIs. For this reason, doctors will generally prescribe tricyclic antidepressants only if previous prescriptions of SSRIs or SNRIs failed to improve symptoms, or for specific symptoms for which they are known to be more effective. Examples of tricyclic antidepressants include imipramine (Tofranil), nortriptyline (Pamelor), amitriptyline, doxepin, and desipramine (Norpramin).
- Monoamine oxidase inhibitors (MAOIs): Like tricyclic antidepressants, MAOIs are generally prescribed only if other medications have failed to work. MAOI use can have serious side effects and must be supported by a strict diet, as interactions with some foods—including certain cheeses, pickles and wines—can be dangerous or even fatal. MAOIs cannot be combined with SSRIs. Examples of MAOIs include tranylcypromine (Parnate), phenelzine (Nardil), and isocarboxazid (Marplan).
- Atypical antidepressants: Antidepressants that don’t fit into the other four classes of medication are grouped into this category. Some common examples of atypical antidepressants include trazodone, mirtazapine (Remeron), vortioxetine (Trintellix), and bupropion (Wellbutrin SR, Wellbutrin XL).
If you’re prescribed an antidepressant medication, be sure to take it only as directed by your doctor.
Don’t take a different dose than what was prescribed and don’t take it for a longer or shorter period of time than recommended by your doctor.
Once you’ve been prescribed an antidepressant, keep in mind that it may take two to eight weeks for the medication to start taking effect.
Some mild side effects can occur within the first two weeks of starting the medication, but many will resolve after that.
Can Antidepressants Cause Weight Loss?
Most antidepressant medications are more commonly associated with weight gain, but there are three that have been connected to weight loss:
Studies on the effect of fluoxetine (Prozac) on weight are varied, with only some people experiencing weight loss. And while it may cause weight loss in the short-term, but after six months or longer can lead to an increase in weight.
Similarly, the research on the impact of duloxetine (Cymbalta) on weight loss is unclear. Duloxetine can decrease appetite, which can lead to weight loss in some people.
However, research has yet to show a compelling and consistent connection between duloxetine (Cymbalta) and weight loss.
Of these three medications, bupropion (Wellbutrin) is the most consistently associated with weight loss.
Several studies, including a 2019 meta-analysis of 27 studies, found that bupropion (Wellbutrin) was the only commonly used antidepressant associated with weight loss.
In the analysis, all of the antidepressants caused an average increase in body weight of 5%, except for bupropion (Wellbutrin).
Bupropion (Wellbutrin), an atypical antidepressant, works by altering the brain chemicals norepinephrine and dopamine.
In addition to being the only antidepressant consistently associated with weight loss, it’s also associated with fewer rates of sexual side effects and sexual dysfunction than SSRIs and SNRIs.
Which Antidepressants Cause Weight Gain?
Though most antidepressants can cause weight gain as side effect, some antidepressants seem more likely to cause weight gain than others, including:
- Amitriptyline (Elavil)
- Imipramine (Tofranil)
- Nortriptyline (Aventyl)
- Paroxetine (Paxil, Pareva)
- Mirtazapine (Remeron)
The effect of SSRIs on weight is mixed.
Despite the fact that many SSRIs cause weight loss during short-term treatment, other studies show that these drugs may cause long-term weight gain. The effects of these drugs will need continued study before we know more.
Why Do Antidepressants Affect Weight?
There are different theories as to why antidepressants affect weight.
Some believe that the medication’s impact on neurotransmitters in the brain have an indirect impact on metabolism.
Others believe that weight gain or weight loss is an indirect side effect of the medications’ efficacy or inefficacy of treating the condition.
For example, some people use food and overeating to cope with anxiety and depression.
In this case, when they start antidepressant medication, they no longer feel the need to eat emotionally, which can lead to weight loss.
The opposite reaction is possible, too. For people who lose their appetite as a result of their depression, effective treatment for their symptoms may help their appetite return, causing a modest weight gain.
Have Antidepressants Ever Been Prescribed for Weight Loss?
Neither weight loss nor weight gain is a guarantee when taking antidepressants.
Like many medications, side effects can vary depending on the patient. Additionally, antidepressant medications have not been approved for weight loss by the Food and Drug Administration (FDA).
Finally, antidepressants can cause rare but serious side effects, including:
- Changes in blood pressure
- Rapid heartbeat
With these potential serious side effects in mind, antidepressants are not prescribed for weight loss.
How to Prevent Weight Loss Due to Antidepressants
When taken as directed, antidepressants can be effective in treating both depression and anxiety.
If you lose an excessive amount of weight after starting an antidepressant, talk to your doctor about the medication’s benefits and side effects.
If the benefits don’t outweigh the weight loss side effects, you can also ask if adjusting the dose—or switching medications—might be helpful. Discuss the pros and cons with your doctor before making such a decision.
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K Health has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations. We avoid using tertiary references.
Anxiety Facts and Statistics. (2020). https://adaa.org/understanding-anxiety/facts-statistics
Antidepressant utilisation and incidence of weight gain during 10 years’ follow-up: population based cohort study. (2018). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5964332/
Is increased antidepressant exposure a contributory factor to the obesity pandemic? (2016). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4872449/
Bupropion: A systematic review and meta-analysis of effectiveness as an antidepressant. (2016). https://journals.sagepub.com/doi/10.1177/2045125316629071
Depression. (2020). https://www.who.int/en/news-room/fact-sheets/detail/depression
Effects of antidepressant and antipsychotic use on weight gain: A systematic review. (2019). https://pubmed.ncbi.nlm.nih.gov/31524318/
What is Anxiety and Depression? (n.d.). https://adaa.org/understanding-anxiety