Mental illness can have a number of unintended consequences ranging from a person’s wallet to their romantic relationship. However, the procedures and medications used to treat mental illness can in themselves carry unexpected–and unwelcome– side effects. One common side effect is weight gain, which can be a distressing body change to undergo in addition to the symptoms of the disorder itself. Antipsychotics (and several antidepressants) are notorious for causing patients to gain weight both in short- and long-term use. There are several theories as to why antipsychotics cause weight gain. In this article, we’ll explore the link between the two as well as how to reverse weight gain from antipsychotics.

The Correlation Between Mental Illness and Weight Gain

Studies have found that 60% of patients with schizophrenia or bipolar disorder are obese. This is not solely the fault of medication, though it may certainly play a role. The symptoms of a mental illness itself can contribute to behaviors that are conducive to weight gains, such as low energy, less motivation to exercise or eat healthy meals, decreased appetite, and poor sleep. Additionally, medications may relieve those same symptoms, reversing the conditions that would prevent weight gain (e.g. decreased appetite), and therefore isn’t a direct result of the medication itself. 

However, that is not to say that antipsychotic-induced weight gain isn’t a valid concern. It’s a side effect that has become a major area of concern amongst clinicians as increased weight can cause a domino effect of negative impact, that can exacerbate the conditions of a mental illness, reduce drug compliance, and overall increase the mortality rate.   

Which Antipsychotics Cause Weight Gain?

Although most types of antipsychotic medications will result in weight gain, they do not all do so to the same degree or by the same mechanism. Certain antipsychotics range in their propensity from high, moderate, to low. They can also vary based on individual characteristics.

High Likelihood of Causing Weight Gain

  • Clozapine
  • Olanzapine

Moderate Likelihood of Causing Weight Gain

  • Chlorpromazine
  • Quetiapine
  • Risperidone
  • Paliperidone

Low Likelihood of Causing Weight Gain

  • Aripiprazole
  • Amisulpride
  • Asenapine
  • Haloperidol
  • Ziprasidone
  • Lurasidone

Why Do Antipsychotics Cause Weight Gain?

This occurrence happens most rapidly during the immediate period after starting antipsychotics (the first few weeks). Weight loss typically slows and evens out over the following months, but depending on the specific medication, the range when weight loss will occur can be as little as 4 months and up to four years. 

Children are particularly prone to gaining weight due to antipsychotic treatment, with up to 80% showing significant weight gain. Some theorize that this is due to their lower body mass index, while others believe it is due to less exposure to antipsychotic medications as compared to adults. Further, children tend to gain more weight than their adult counterparts.

Reduced Glucose Metabolism

One reason for this is that antipsychotic medications reduce the body’s ability to metabolize glucose and increase cholesterol and triglyceride levels, which in turn causes hypertension. This cluster of side effects causes what’s known as metabolic syndrome, which makes a person’s risk of diabetes five times higher, and their risk of cardiovascular illness two times higher. 

Hormone Receptors

However, the cause of weight gain may vary depending on the particular type of antipsychotic. Largely, the way they act with specific receptors: serotonin 5-HT2A and 5-HT2C, dopamine D2 and D3, histamine H1, and muscarinic M3.


Neuropeptides leptin and adiponectin play a direct role in managing appetite control and energy metabolism and are directly affected by antipsychotic medications. 

Leptin is a hormone released by body fat that is responsible for providing the sensation of feeling full (this is different from the feeling of hunger which is triggered by the hormone ghrelin). Adiponectin plays a more complex role in regulating inflammatory responses and insulin sensitivity, and can also improve glucose and lipid metabolization. Obesity is associated with high levels of leptin and low levels of adiponectin.

Antipsychotic treatments increase leptin and reduce adiponectin, thus creating hormonal cues that result in individuals eating more and being less efficient in metabolizing the food.


Individuals may experience varying levels of weight gain due to their genes. A study found nine specific genes that were most strongly associated with a person’s propensity for gaining weight when taking antipsychotic medications. These genes are Single-nucleotide polymorphisms related to ADRA2A, DRD2, 5-HTR2C, and MC4R.

How To Reverse Weight Gain From Antipsychotics

Both pharmacological and nonpharmacological methods are used to manage weight gain caused by antipsychotic medications, though weight gain may not be possible to avoid completely. Switching medications or adjusting the dosage can be used to prevent weight gain. However, the efficacy of this approach has yet to be thoroughly examined and should not come at the expense of treating mental illness. Counseling and behavioral interventions are much more widely used for weight reduction, rather than the preventive approach. Find a mental health rehab near you to speak to a professional about which method is right for you. 

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