Can Antidepressants Like Paxil Cause Weight Gain?

Dr. Christopher McGowan
December 23, 2022

It is estimated that nearly 5% of the adult population in the United States suffers from regular feelings of depression and over 8% of adults have had at least one episode of major depression over the preceding 12 months. Though many people who are dealing with depression never seek treatment, those that do are often prescribed antidepressant medications to manage the condition. While effective for some people, these medications also tend to carry a variety of side effects that have to be weighed against the potential benefits. One of the side effects often seen with the antidepressant drug Paxil is weight gain.   

What Is Paxil?   

Paxil is a trade name for paroxetine, one of the most commonly prescribed antidepressants in the United States. Paroxetine is in a class of drugs called selective serotonin reuptake inhibitors (SSRIs); other common examples include citalopram (Celexa), fluoxetine (Prozac), sertraline (Zoloft), and escitalopram (Lexapro). SSRIs like paroxetine are used to treat mild to moderate depressive symptoms as well as major depressive disorder, anxiety disorders, panic disorders, mood disorders, and other mental health problems. Paroxetine was first approved by the FDA for medical use in 1992. 

What Are SSRIs and How Do They Work?          

The brain uses chemicals called neurotransmitters to send messages between the synapses of nerve cells; these messages affect how the brain works, how the body functions, and how we think and feel. Each nerve has receptors that can receive information in the form of neurotransmitters and then continue to relay the signal to other nerve cells. Some of the neurotransmitters are lost in the process, but most of them are reabsorbed by the cell that initially transmitted it; this reabsorption is referred to as “reuptake.” 

SSRIs are so named because they inhibit the reuptake of a particular neurotransmitter—serotonin—in order to increase the amount present in the synaptic gap between nerve cells. Serotonin is a complex monoamine neurotransmitter that is thought to be involved in numerous aspects of body physiology like cognition, learning, memory, learning, sleep, and body temperature. It is also thought to play a major role in mood and emotion, and a lack of sufficient serotonin is presumed to be one of the factors in major depression and other related disorders. 

SSRIs are just one of several different medications that are used to treat depression and related disorders. Serotonin and norepinephrine reuptake inhibitors (SNRIs) like venlafaxine (Effexor) and duloxetine (Cymbalta) are a newer form of antidepressant that work in a similar way as SSRIs but they block the reuptake of norepinephrine in addition to serotonin. Tricyclic antidepressants (TCAs) like nortriptyline (Pamelor) and amitriptyline (Elavil) are an older type that also affect neurotransmitters but are less selective and therefore tend to have more side effects.

Side Effects of Paxil    

Like other medications used to treat depression, Paxil is a tool for managing depressive symptoms rather than a cure. Doctors sometimes have to prescribe several different types of medication to find the right match for each person, and that often involves weighing potential side effects against the benefits of the drug. Because of their ability to selectively inhibit serotonin and not other neurotransmitters, SSRIs often have fewer adverse effects than other options. Nevertheless, there are some known common side effects: 

  • headaches
  • difficulty sleeping
  • weakness or fatigue 
  • gastrointestinal problems like diarrhea or constipation
  • nervousness or restlessness 
  • nausea or vomiting  
  • reduced sex drive 
  • dry mouth
  • dizziness 
  • weight changes 
  • loss of appetite 
  • drowsiness or yawning 

Many of the common side effects experienced by patients are mild and tend to resolve on their own with continued treatment. In rare cases, however, paroxetine can lead to suicidal thoughts or mania. Ongoing headaches or persistent weakness and confusion may also be signs of low blood sodium levels and warrant contacting a doctor. In very rare cases, the medication can cause serotonin syndrome, a collection of additional symptoms that arises from too much serotonin being in the body. 

Paxil and Weight Gain

One of the other known side effects of SSRIs in general is weight gain, though there is some evidence that it’s even more likely with paroxetine. According to one study in the Journal of Clinical Psychiatry, subjects on paroxetine gained significantly more weight than those who were taking fluoxetine or sertraline; in the study, the subjects on paroxetine experienced a 7% increase in body weight. However, there is still a lower risk of weight gain with SSRIs than older tricyclic antidepressants or tetracyclic antidepressants (TeCAs) like mirtazapine (Remeron).

How Does Paxil Lead to Weight Gain?  

The precise reason paroxetine leads to weight gain isn’t entirely clear, but there are likely lifestyle factors associated with depression that may have an impact. For instance, poor diet, insufficient physical activity, and smoking or drinking can all potentially increase the likelihood of gaining weight even apart from the side effects of medication. It may also be related to the effects of coming out of depression. Often when people are depressed, they lose their appetite and eat less; then, when they start taking medication and feel better, their appetite returns and they end up inadvertently overeating

Another possible reason for the connection between paroxetine and weight gain is related to its effect on serotonin. As noted above, serotonin is involved in many physiological processes, including those that impact hunger and satiety. In the short term, the increase in serotonin levels may increase satiety and less eating. Over the long term, however, there can be a downregulation of serotonin receptors that leads to cravings for carbohydrate-rich foods in particular. Overindulgence in these foods can then lead to weight gain. 

The Bottom Line

Can Paxil cause someone to gain weight? The best answer to the question is: possibly. Research does seem to show a correlation between taking the medication and an increase in body weight. The mechanism for how the weight gain occurs is still very uncertain, however, and that means it’s unclear if the drug itself is entirely to blame. The available data suggests that only 10% of users are likely to gain weight when taking the medication for an extended period of time. Still, though, if you are taking it and notice a weight increase, you can always talk to your doctor about switching to a different medication. 

Finding a Weight Loss Solution 

Whatever the main cause of an increase in body weight, losing it again is an entirely different proposition. While a healthy diet and increased physical activity are the traditional answer for weight loss, most people don’t find lasting success. That’s why at True You Weight Loss, we are passionate about providing an alternative solution that can help you lose the weight and keep it off over the long term. If you’d like to learn more about our non-surgical weight loss procedures, please contact us today to request a consultation.

Dr. Christopher McGowan
Dr. Christopher McGowan

Dr. Christopher McGowan, MD, a leader in endobariatrics, specializes in non-surgical obesity treatments and is triple-board-certified in Internal Medicine, Gastroenterology, and Obesity Medicine. Renowned for pioneering endoscopic sleeve gastroplasty (ESG) with over 2,000 procedures, his global influence and research contributions define him as a top expert.

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