Weight and Mental Health

Why Do People Gain Weight on Psych Meds?

Max Carmody, MSc

People gain weight on psychiatric medication due to increases in appetite and craving for carbohydrate rich food, decreased physical activity due to sedating effects of the medication, and changes in metabolism.

Types of Psychiatric Medications

There are four main types of psych meds. They are antidepressants, antipsychotics, sleeping pills and minor tranquilizers, and lithium and other mood stabilizers. We’ll give a brief definition of each of the types.

Antidepressants are psychiatric drugs that are licensed to treat depression, sometimes they are also used to treat anxiety disorders, phobias, or things like long term pain. Antidepressants work by boosting the activity of particular brain chemicals. This includes noradrenaline and serotonin, neurotransmitters which are thought to be involved in regulating your mood.

Antipsychotics are for treating psychosis. They are prescribed for things like schizophrenia, schizoaffective disorder, some forms of bipolar, severe depression, and the psychotic symptoms of personality disorder. Antipsychotics don’t cure psychosis but can help to reduce and control different psychotic symptoms, such as delusions and hallucinations, confusion, or mania. There are multiple explanations of why antipsychotics help. They may block the action of dopamine, some scientists  believe that psychosis is caused by your brain producing too much dopamine. They may affect other brain chemicals such as serotonin or glutamate.

Sleeping pills and minor tranquilizers are sedative medications. They slow down the functions of your body and brain. They are prescribed for severe anxiety or insomnia. They are usually prescribed to reduce symptoms of anxiety, such as feeling agitated or shaky. 

Mood stabilizers are generally used for bipolar disorder, mania and hypomania, or recurrent, severe depression or schizoaffective disorder. Some of the individual drugs called mood stabilizers are actually very different chemicals. The three main drugs used as mood stabilizers are lithium, anticonvulsants, and antipsychotics. Some people assume that antidepressant drugs are also mood stabilizers, however, they are not.

Which Drugs Cause the Most Weight Gain

Olanzapine (Zyprexa) and Clozapine (Clozaril) may be the two worse types of medications for weight gain. Some studies have shown that on average these drugs may cause patients to gain more than 8 pounds in just 10 weeks. Risperidone and quetiapine are also pretty bad. These are antipsychotics, antipsychotics generally cause people to gain more weight than other types of psychiatric drugs.

Antidepressants can also cause weight gain. The antidepressants with the highest risk of causing weight gain are “amitriptyline, citalopram, mirtazapine, nortriptyline, trimipramine, paroxetine, and phenelzine”.

Why Do Psychiatric Drugs Cause Weight Gain?

Weight gain commonly occurs from antidepressant, mood-stabilizing, antipsychotic and other medicines for different psychiatric disorders, as we’ve discussed. The effect of the medicines on body weight actually depends on which type of medication class, with some more likely to cause weight gain than others. There are different ideas behind why they cause weight gain. Some doctors think that it is a result of increased appetite, and craving carbs. Psychotropic medications are often sedating, so they may result in lower rates of physical exercise, which can lead to weight gain.

There is actually not that much information out there on the causes of weight gain from psychiatric drugs. And the research is pretty inconclusive and incomplete. Although some doctors say that all the weight gain comes from increased appetite, and maybe decreased exercise, I personally know that this is not true. I took one drug for just a few weeks, and I gained over 10 pounds during this period, maybe even 15 or so. I was carefully watching what I ate during this period, and I was exercising a lot. And I don’t remember even craving more food. So I believe that there is another cause. Perhaps it affected my metabolism. 

Weight gain, is a well established side effect of almost all antipsychotics. People with a serious mental illness (SMI) tend to quickly gain weight within the first few weeks of starting a new drug. This then usually gradually decreases and flattens within a year. Genetic factors play a very important role in weight gain due to medication. It is estimated that genetic factors are responsible for 60-80% of the weight gain.

Why Do Antidepressants Cause Weight Gain?

Medications like the antidepressants discussed above increase serotonin levels in the brain. Serotonin is responsible for regulating mood and affecting the appetite. Short term use of antidepressants may reduce impulsivity and increase satiety, which can actually reduce the amount of food somebody is eating and even cause weight loss. However, long term use of over a year can cause serotonin receptors to be downregulated. This leads to cravings for carbohydrate rich foods like sweets, bread, and pasta, and this can lead to weight gain.

Why Do Antipsychotic Medications Worsen Diseases Related to Obesity?

Similar to antidepressants, antipsychotics will affect the chemical messengers in the brain that are associated with energy metabolism and appetite control. These messengers include dopamine, serotonin, histamine, and muscarinic receptors. Antipsychotics can increase cholesterol and triglyceride levels, impair the metabolism of glucose, and cause hypertension. All of this can worsen obesity related diseases.

If you are struggling with mental health, and would like to learn more about how medication can help you out, you can get a concise e-book on the topic here.

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