Nearly 1 in 5 U.S. adults are dealing with an anxiety disorder in any given year, according to the National Institute of Mental Health. Antianxiety medications are sometimes used as a component of anxiety disorder treatment. These medicines alter the levels of various chemical messengers in the brain, which can lead to reduced anxiety and related symptoms. As with any medicine, antianxiety medications can have side effects. Reduced appetite and weight loss are not common side effects with medications used to treat anxiety, but can occur in some people taking certain drugs. Weight loss related to antianxiety medication is usually minimal and rarely a cause of concern.
Drugs in the benzodiazepine medication group act as central nervous system depressants, meaning they tamp down brain activity. This effect makes benzodiazepines useful as sedatives, sleep aids, anticonvulsants and antianxiety medications. Common examples include alprazolam (Xanax), diazepam (Valium), lorazepam (Ativan), triazolam (Halcion) and clonazepam (Klonopin). Benzodiazepines act quickly, usually taking effect within a few minutes to an hour after an oral dose. Nausea, dizziness, vomiting, stomach upset and over-sedation are possible side effects that might lead to weight loss. However, benzodiazepines are not typically recommended for long-term use to manage anxiety because of the high risk for dependence and addiction. Significant weight loss is unlikely with short-term benzodiazepine treatment.
Venlafaxine and Desvenlafaxine
Venlafaxine (Effexor) and desvenlafaxine (Pristiq) are closely related medicines in the serotonin and norepinephrine reuptake inhibitors (SNRIs) drug class. Like other SNRIs, venlafaxine and desvenlafaxine are used to treat depression. Venlafaxine has also been approved by the U.S. Food and Drug Administration for the treatment of generalized anxiety disorder, panic disorder and social anxiety disorder. As of 2016, desvenlafaxine has not been FDA approved for the treatment of anxiety disorders, but some doctors prescribe it for this purpose. These drugs do not have immediate antianxiety effects, but may alter the chemical balance in the brain leading to decreased symptoms from an anxiety disorder over several weeks to months. Decreased appetite leading to weight loss has been reported as a possible side effect of both venlafaxine and desvenlafaxine. However, this effect is uncommon and the amount of weight loss is typically inconsequential in terms of overall health status.
Buspirone is an antianxiety drug first approved by the FDA in 1986 for the treatment of anxiety disorders. The drug differs chemically from the benzodiazepines, is less sedating, and does not cause dependence leading to potential addiction. Unlike the fast-acting benzodiazepines, buspirone's antianxiety effects are not realized for several weeks. Therefore, the drug is not helpful for treating acute anxiety. Buspirone can have gastrointestinal side effects, including nausea, vomiting, dry mouth, upset stomach, constipation and diarrhea. These side effects -- which are uncommon and often decrease over time -- could potentially lead to weight loss.
Older antidepressants drugs called monoamine oxidase inhibitors (MAOIs) are sometimes prescribed to treat certain anxiety disorders if other treatments and medications have been ineffective. Examples include phenelzine (Nardil) and tranylcypromine (Parnate). Like newer antidepressants, MAOIs alter the balance of chemical messengers in the brain, which might lead to reduced anxiety disorder-related symptoms. Some weight loss is possible with MAOIs due to side effects such as nausea, dry mouth and stomach upset. However, weight gain is more common with these medicines. Dietary restrictions are necessary while taking an MAOI, so this might be factor in losing weight for some people.
Talk With Your Doctor
Doctors and therapists create individualized treatment plans for people living with an anxiety disorder. Medications other than those mentioned might be recommended in some cases, which could potentially affect your appetite and weight. If you experience weight loss while being treated for anxiety, talk with you doctor to determine whether it's related to your medication or possibly another medical condition. This is especially important if you experience new symptoms along with the weight loss.
Reviewed and revised by: Tina M. St. John, M.D.