Zoloft (sertraline) may lead to a small weight gain ranging from 1% to 1.6% of initial body weight when used over 6 months to 1 year. For example, in a 150 lb (68 kg) person, this would equal an added 1.5 to 2.4 lbs (0.7 to 1.1 kg) of weight. Shorter-term treatment in adults usually does not lead to substantial weight gain, but most patients need to take Zoloft for an extended period of time.

In children, weight loss has been reported with Zoloft possibly due to side effects like nausea or loss of appetite. In 281 children treated with Zoloft, at least 2% reported decreased weight, at a rate that was twice that of placebo (an inactive pill).

Zoloft is a selective serotonin reuptake inhibitor (SSRI) approved to treat

• Depression
• Obsessive-compulsive disorder
• Panic disorder
• Post-traumatic stress disorder
• Social anxiety disorder
• Premenstrual dysphoric disorder

How does weight gain with Zoloft compare to other SSRIs?

Of the SSRIs, Zoloft (sertraline) and Prozac (fluoxetine) appear to cause the least amount of weight gain.

Weight gain with SSRI treatment can vary. In general, weight gain is ranked:

• lowest with fluoxetine
• slightly higher with sertraline (Zoloft), citalopram (Celexa), escitalopram (Lexapro) and fluvoxamine (Luvox)
• highest with paroxetine (Paxil).

In a 26 to 32 week double-blind study, 284 patients with major depressive disorder were randomly assigned to long-term treatment with fluoxetine (Prozac), sertraline (Zoloft), or paroxetine (Paxil).

• Of the three SSRIs, paroxetine-treated patients had a significant weight gain, sertraline-treated patients had a modest but nonsignificant weight gain, and those receiving fluoxetine had a nonsignificant weight loss.
• The number of patients whose weight increased 7% or more from the start of the study was significantly greater for paroxetine-treated patients than for those receiving either fluoxetine or sertraline.

In another 2.5 year open-label study of 138 patients treated for obsessive-compulsive disorder (OCD), weight changes were assessed for several SSRIs (citalopram, fluoxetine, fluvoxamine, paroxetine, or sertraline), as well as the tricyclic antidepressant (TCA) clomipramine.

• In all groups except fluoxetine, a significant weight gain was reported. Clomipramine (a TCA) was associated with the greatest weight gain. TCAs are well known to cause more weight gain than SSRIs.
• Of the SSRIs, fluoxetine (Prozac) and sertraline (Zoloft) had the lowest weight gain.
• Zoloft and Prozac also had the lowest percentage of patients with a weight gain of 7% or more over their initial body weight (4.5% for Zoloft and 8.7% for Prozac).

Do all antidepressants cause weight gain?

Treatment with antidepressants and selective serotonin reuptake inhibitors (SSRIs) in general tend to cause weight gain with long-term treatment (more than one year). Overall weight changes depend upon which antidepressant you use. Most antidepressants lead to only modest weight gain which can be addressed with diet and exercise.

• Older antidepressants like the tricyclic antidepressants (TCAs), for example amitriptyline or doxepin, cause more weight gain than the SSRIs but are infrequently prescribed today for depression.
• Mirtazapine (Remeron), a tetracyclic antidepressant, is known to be associated with significant weight gain. In studies, appetite increase was reported in 17% of patients treated with Remeron, and 7.5% of patients had a weight gain of at least 7% compared to the start of the study.
• In contrast, bupropion (Wellbutrin SR, Wellbutrin XL), an atypical antidepressant, is often linked with weight loss. In studies, between 14% and 19% of patients taking bupropion loss at least 2.2 kg (5 lb) compared to 6% on an inactive placebo.

A large cohort study (136,762 men and 157,957 women) in the United Kingdom looked at electronic health records to evaluate the long-term association between antidepressant prescribing and weight gain. Over 90% of patients had a diagnosis of depression.

Researchers looked at data over a 10-year period to determine the incidence of at least a 5% increase in body weight, and the number who transitioned (based on body mass index) to a status of overweight or obese.

• In the year of study entry, 13% of men and 22.4% of women (mean age of 51.5 years) were prescribed antidepressants, but may have had other diagnoses besides depression.
• Over the follow-up period, those prescribed an antidepressant had an increased risk of at least a 5% gain in body weight compared to those who were never prescribed an antidepressant.
• Weight gain substantially increased in the second and third years of treatment. During the second year of treatment, the risk of at least a 5% weight gain was found to be 46.3% higher than in a general population comparison group. Those originally classified as normal weight were more likely to transition to an overweight or obese category.
• Researchers concluded that antidepressant treatment was associated with a sustained increase in risk of weight gain over at least 5 years.

Why does Zoloft cause weight gain?

• It is not fully clear if weight gain with antidepressants and Zoloft in particular is due to an increased appetite after recovery from a mental health disorder, due to the medicine itself, or some other factor.
• Antidepressants may cause weight gain by interfering with serotonin or histamine neurotransmitters in the brain that control appetite.
• Some antidepressants may cause drowsiness or fatigue that lower levels of activity, leading to weight gain.