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Does mirtazapine cause weight gain?

Mirtazapine may cause increased appetite and weight gain
By | Sep. 11, 2024
An analog scale: Does mirtazapine cause weight gain?

Key takeaways

  • Mirtazapine is an atypical antidepressant approved by the FDA to treat depression in adults.

  • Mirtazapine has many potential side effects, two of which are increased appetite and weight gain.

  • The amount of weight you can gain from mirtazapine will vary depending on the individual. In studies, those who gained weight from mirtazapine experienced a weight gain of 7% or more of their body weight.

  • To avoid weight gain from mirtazapine, it’s important to maintain a healthy diet, stay physically active, limit stress, and get adequate sleep.

In this article:

Commonly referred to by its brand name Remeron, mirtazapine is a prescription drug approved by the U.S. Food and Drug Administration (FDA) to treat major depressive disorder (depression) in adults, and it is sometimes used off-label as an appetite stimulant. It belongs to a class of drugs called tetracyclic antidepressants and works by increasing the levels of serotonin and norepinephrine in the brain. 

While it is a first-line medication for depression, mirtazapine has many potential side effects, two of which are increased appetite and weight gain. 

Can mirtazapine cause weight gain?

Mirtazapine is known to increase appetite and cause weight gain whether it’s taken as a short- or long-term treatment. 

  • In clinical trials, weight gain was a common side effect of mirtazapine in 12% of people. 
  • In a 2011 Cochrane review, researchers concluded mirtazapine was more likely to cause drowsiness and weight gain in comparison to other antidepressants. 
  • A small 2006 study concluded that mirtazapine was associated with significantly increasing body weight, body fat mass, and leptin concentration.
  • A 2001 clinical study found that 21% of self-reported weight gain occurred after 12 weeks of mirtazapine treatment. 

Why does mirtazapine cause weight gain?

It’s unclear how mirtazapine causes weight gain, but a few hypotheses exist. The first is that its effects are due to its blockage of specific serotonin (5-HT2) and histamine (H1) receptors. Another hypothesis is that mirtazapine’s increase in fat mass results in higher leptin concentrations. Leptin is a hormone released by body fat that regulates satiety. It prevents hunger by telling your body that it’s full. However, as levels increase, you can develop leptin resistance, and your body may not feel as full as it should. This causes you to feel hungrier than normal and may cause persistent cravings. While these hypotheses explain mirtazapine’s mechanism behind weight gain, more research is needed to understand fully why it causes this side effect. 

How much weight do you gain on mirtazapine?

The amount of weight you can gain from mirtazapine will vary depending on the individual. According to the drug’s prescribing information, those who gained weight from mirtazapine experienced a weight gain of 7% or more of their body weight. This means a 150 lb adult may gain about 11 lbs or more while taking mirtazapine. Another study from the Journal of Clinical Psychiatry reported an average weight gain of 8 pounds over six weeks of mirtazapine treatment. 

How to avoid weight gain with mirtazapine

Because weight gain is a well-known side effect of mirtazapine, your healthcare professional will likely provide medical advice to help you avoid weight gain. Depending on your medical history, other medications, and lifestyle, they can help formulate a specific plan to prevent weight gain. Strategies may include: 

  • Eating a healthy diet that consists of whole foods. Optimize your diet by consuming healthy fats, lean proteins, vegetables, fruits, low-fat dairy, and whole grains. Because mirtazapine increases your appetite, making healthy food choices can help limit any potential weight gain from the drug. 
  • Limiting processed foods and sugars. Part of a healthy diet includes limiting the intake of processed foods and foods with added sugars. These foods are often high in calories, which can lead to even more weight gain. Therefore, consuming these foods in moderation is key. 
  • Exercising regularly. Regular physical activity is key to avoiding weight gain. It helps you burn calories to counteract any increase in appetite you may experience during mirtazapine treatment since mirtazapine has sedative properties.
  • Limiting stress. Not only can stress worsen depression, but it can also cause you to change your eating habits and affect how your body stores fat. This can cause weight gain. 
  • Obtaining adequate sleep. Sleep deprivation has been linked to a higher risk of weight gain. Practicing good sleep hygiene is another way to limit weight gain from mirtazapine. 
  • Discuss possible mirtazapine alternatives. While mirtazapine is an effective antidepressant to aid in various treatments for mental health conditions, there are many antidepressants available on the market. Your healthcare provider can discuss drugs that are less likely to cause weight gain in comparison to mirtazapine. 

Alternatives to mirtazapine

Despite being a first-choice treatment for depression, mirtazapine may not be right for everyone. Mirtazapine-induced weight gain can be very detrimental to people with certain medical conditions. It can worsen conditions such as high cholesterol, heart disease, and type 2 diabetes, or it can increase the risk of serious medical conditions, including obesity, stroke, or cancer. 

Fortunately, several alternative antidepressant medications are available. The following table lists alternative medicines for depression. 

Mirtazapine alternatives
Drug SingleCare price
Zoloft (sertraline) See latest prices
Prozac (fluoxetine) See latest prices
Lexapro (escitalopram) See latest prices
Celexa (citalopram) See latest prices
Effexor XR (venlafaxine) See latest prices
Cymbalta (duloxetine) See latest prices
Paxil (paroxetine) See latest prices
Viibryd (vilazodone) See latest prices
Trintellix (vortioxetine) See latest prices

Weight gain is a common side effect of several antidepressants. A 2024 study in the Annals of Internal Medicine provided some insight into which antidepressants cause the most weight gain. Researchers interpreted data from over 183,000 participants and compared the weight-related effects of eight antidepressants. The study found that bupropion was associated with the lowest risk of weight gain, while escitalopram, paroxetine, and duloxetine were associated with the highest risk. However, it’s important to note that mirtazapine wasn’t included in this study.