Antidepressants are a common treatment for helping to reduce symptoms of anxiety. For many, these medications allow them to better function throughout the day. For some, severe anxiety and depression symptoms would prevent them from going to work or functioning in daily life if they were not able to take medication.

But along with the benefits of antidepressants, there are also side effects. One such side effect is weight gain. Approximately 25 percent of people taking antidepressants experience weight gain of 10 pounds or more. Weight gain is most often associated with long term use of medications. People taking antidepressants for eight to twelve weeks didn't experience much weight gain. An article published in 2003 in the Cleveland Journal of Medicine indicated weight gain was more probable after 6 months or more of continued use of antidepressants.

Why Do Antidepressants Cause Weight Gain?

The exact reason why antidepressants may cause individuals to gain weight is not known, however, there are a number of theories:

• Antidepressants may slow down metabolism. This could explain why some people feel they are not eating more, but are still gaining weight or may be eating more but it would not explain the amount of weight they are gaining.
• Some people do eat more, stating they never feel satisfied, even right after eating a meal. Some people indicate they have developed a craving for carbohydrates.
• Another theory is that the antidepressants worked, meaning that previous feelings of depression or anxiety had lessened the appetite and reduced the desire for food. When a person begins to feel better, they once again enjoy and therefore desire food.

Recent research has shown that people that gain weight in the first week after taking antidepressants will continue to gain weight. You may want to monitor your weight right from the beginning.

Which Medications Cause Weight Gain?

Not all antidepressants cause weight gain, although the most popular group of medications for treating anxiety, SSRI (selective serotonin reuptake inhibitor) medications seemed to cause the most weight gain. This group would include medications such as Prozac, Zoloft, Lexapro and Paxil.

Research has shown that Paxil causes the most weight gain. Although weight gain will vary based on the individual, some people taking Paxil have reported weight gains of between 20 and 50 pounds. Zoloft, Remeron and Luxox have also been reported to cause significant weight gain, according to Janet Kinosian in an article entitled, "Antidepressants & Weight Gain."

Tricyclic antidepressants (Elavil, Tofranil) and MAOI (Parnate, Nardil) also increase the chance of gaining weight, both in short-term use and long-term use. These medications are thought to slow down metabolism rates, causing an increase in weight unless you change your diet to match your metabolism.