SSRIs, Weight Gain and Cholesterol: Minimizing Risk with Precision Medicine

Many people worry about gaining weight on antidepressants. Large recent studies show that antidepressants can also affect cholesterol, triglycerides and blood sugar, which matter for long-term heart and metabolic health. Here we explain what these studies found, how genetic differences in drug metabolism may play a role, and what you and your doctor can do to lower the risk.

Two liver enzymes, CYP2C19 and CYP2D6, break down most antidepressants. Genetic differences in these enzymes are known to affect how well antidepressants work and how well they are tolerated. Researchers are now also studying how these genes relate to weight, cholesterol, triglycerides and blood sugar.

Should you stop your antidepressant if you gain weight?

Not on your own. Stopping an antidepressant suddenly can cause withdrawal symptoms and a return of depression or anxiety. Talk to your doctor or pharmacist first. They can review your dose, consider another medication, and check your weight, cholesterol and blood sugar.

Antidepressants, drug metabolism and weight gain

Body weight depends on many factors, including diet, physical activity, sex, genetics and the condition being treated, so it is hard to link weight gain to one medication. Weight changes differ between antidepressants. Older antidepressants, such as tricyclics, are more likely to cause weight gain than SSRIs and SNRIs as groups, but individual medications vary. Duloxetine can cause some weight loss early in treatment, and bupropion may lead to weight loss in some people.

Among SSRIs, paroxetine and citalopram are linked to the most weight gain in children and adolescents, and higher doses are linked to greater gains. In young people, weight gain on citalopram and escitalopram may also be related to how quickly the CYP2C19 enzyme breaks them down.

An international expert consensus concluded that current evidence supports CYP2C19 and CYP2D6 testing to guide the choice and dose of several antidepressants. For people who have these results, the 2023 Clinical Pharmacogenetics Implementation Consortium (CPIC) guideline explains how to adjust antidepressant selection and dosing. Knowing your genetic profile can help you and your doctor find a medication and dose with a lower risk of side effects.

Antidepressants, cholesterol and triglycerides

Triglycerides are fats that store unused calories and provide energy. Diets high in sugar, refined starch and fat can raise them, and high triglycerides are linked to heart disease and diabetes.

A 2023 study of more than 36,000 people taking antidepressants in the UK Biobank found that amitriptyline, fluoxetine, citalopram, escitalopram, sertraline, paroxetine and venlafaxine were all linked to higher total cholesterol, LDL ("bad") cholesterol and triglycerides, and lower HDL ("good") cholesterol. Venlafaxine had the least favourable lipid profile. Antipsychotics were linked to lower HDL cholesterol and higher triglycerides.

The study also looked at genes. Among people taking sertraline, CYP2C19 intermediate metabolizers had slightly better results, with higher HDL cholesterol and lower triglycerides, than normal metabolizers. The researchers suggested regular cholesterol checks for people taking antidepressants. Because the study was observational, it shows links rather than proof of cause.

HbA1c, insulin resistance and diabetes

HbA1c is a blood test that reflects average blood sugar over about three months and is used to diagnose and monitor diabetes. A UK Biobank study of more than 31,000 people taking antidepressants found that:

• CYP2D6 poor metabolizers taking paroxetine had higher HbA1c than normal metabolizers.
• Among people with diabetes taking venlafaxine, CYP2D6 poor metabolizers had much higher HbA1c than normal metabolizers.
• Among people with diabetes taking fluoxetine, CYP2D6 intermediate metabolizers had lower HbA1c.

These findings fit existing guidelines: for CYP2D6 poor metabolizers, CPIC recommends half the usual dose of paroxetine and considering another medication instead of venlafaxine. For people with type 2 diabetes, metformin is usually the first medication used to lower blood sugar. If more help is needed, add-on therapies such as GLP-1 medications (for example, semaglutide) can lower blood sugar and also support weight loss. Learn more in Weight loss medications: what you need to know.

Lifestyle tips to help prevent weight gain while taking antidepressants

Prevent overeating: Coming to the table very hungry can lead to overeating. Avoid skipping meals and keep healthy snacks on hand between meals.

Mindful eating: Mindful eating means paying close attention to the physical and emotional sides of eating. It can help prevent overeating and encourage nourishing food choices. Try pausing for a moment before eating, chewing thoroughly and eating slowly without distraction. Learn more about mindful eating.

Exercise: Regular physical activity, including both aerobic and resistance training, helps regulate weight, reduces spikes in blood sugar, lowers the risk of heart disease and improves mood. For example, try a 30-minute walk or some squats after meals.

Overall eating patterns

• Build meals and snacks around at least two of these: fibre, healthy fats and high-quality protein. This helps you feel full and prevents spikes in blood sugar.
• Cut back on simple carbohydrates, especially added sugars and foods with high-fructose corn syrup, to help lower triglycerides.
• The Mediterranean diet balances complex carbohydrates, protein and healthy unsaturated fats. It has been shown to lower the risk of heart disease and may support mental health.
• A ketogenic diet (high fat, low carbohydrate) may not be the best choice, because it can raise cholesterol further in some people.

What can you do to get effective treatment and lower long-term risks?

1. Consider a pharmacogenetic test to help choose your antidepressant and dose. Matching medications and doses to your DNA can reduce the risk of side effects. Switching to a different SSRI or another antidepressant may help.
2. Once you have your results, review them with a pharmacist who has expertise in pharmacogenetics.
3. Even if your weight is normal, ask your doctor about checking your cholesterol, triglycerides and HbA1c, and adjusting your treatment if any of them is above the normal range.
4. If diet and exercise are not enough, your doctor may recommend cholesterol-lowering medication. For people with type 2 diabetes, metformin and add-on therapies such as GLP-1 medications can help control blood sugar and support weight management.

Frequently asked questions

Do SSRIs cause weight gain?

Some do, especially with long-term use and higher doses. Paroxetine and citalopram are among the SSRIs most linked to weight gain, while older antidepressants such as tricyclics are more likely to cause weight gain overall.

Can antidepressants raise cholesterol?

Yes. In a large UK study, several common antidepressants were linked to higher cholesterol and triglycerides, with venlafaxine showing the least favourable profile.

Can a pharmacogenetic test help reduce side effects?

Yes. CYP2C19 and CYP2D6 results can guide the choice and dose of several antidepressants, which can lower the risk of side effects.

Should I have my cholesterol and blood sugar checked if I take an antidepressant?

It is a good idea to ask your doctor. Researchers have suggested regular cholesterol monitoring for people taking antidepressants.

References

Richards-Belle A, Austin-Zimmerman I, Wang B, et al. Associations of antidepressants and antipsychotics with lipid parameters: Do CYP2C19/CYP2D6 genes play a role? A UK population-based study. J Psychopharmacol. 2023;37(4):396-407.

Austin-Zimmerman I, Wronska M, Wang B, et al. The Influence of CYP2D6 and CYP2C19 Genetic Variation on Diabetes Mellitus Risk in People Taking Antidepressants and Antipsychotics. Genes (Basel). 2021;12(11):1758.

Strawn JR, Mills JA, Poweleit EA, Ramsey LB, Croarkin PE. Adverse Effects of Antidepressant Medications and their Management in Children and Adolescents. Pharmacotherapy. 2023;43(7):675-690.

Sepúlveda-Lizcano L, Arenas-Villamizar VV, Jaimes-Duarte EB, et al. Metabolic Adverse Effects of Psychotropic Drug Therapy: A Systematic Review. Eur J Investig Health Psychol Educ. 2023;13(8):1505-1520.

Bousman CA, Bengesser SA, Aitchison KJ, et al. Review and Consensus on Pharmacogenomic Testing in Psychiatry. Pharmacopsychiatry. 2021;54(1):5-17.

Bousman CA, Stevenson JM, Ramsey LB, et al. Clinical Pharmacogenetics Implementation Consortium (CPIC) Guideline for CYP2D6, CYP2C19, CYP2B6, SLC6A4, and HTR2A Genotypes and Serotonin Reuptake Inhibitor Antidepressants. Clin Pharmacol Ther. 2023;114(1):51-68.

Oh RC, Trivette ET, Westerfield KL. Management of Hypertriglyceridemia: Common Questions and Answers. Am Fam Physician. 2020;102(6):347-354.