They can cause depression, anxiety and other problems…

It’s hardly news that supplements—just like drugs—can have physical side effects.

Recent development: Researchers are now learning more and more about unwanted mental changes that can occur when taking popular supplements (such as herbs and hormones).

These supplements can be a hidden cause of depression, anxiety, mania and other mental changes because patients—and their doctors—often don’t realize how these products can affect the brain.

Supplements that may cause unwanted mental changes…


Melatonin is among the most popular supplements for treating insomnia, jet lag and other sleep disorders. Melatonin is a natural hormone that’s released by the pineal gland at night and readily enters the brain. Unlike many sleep aids, it doesn’t render you unconscious or put you to sleep—it causes subtle brain changes that make you “ready” for sleep.

Studies have shown that people who take melatonin in the late afternoon or early evening tend to fall asleep more quickly when they go to bed. The amount of melatonin used in scientific studies ranges from 0.1 mg to 0.5 mg. However, the products in health-food stores typically contain much higher doses—usually 1 mg to 5 mg. Supplemental melatonin also may become less effective over time, which encourages people to increase the doses even more.

Effects on the brain: In people with depression, melatonin may improve sleep, but it may worsen their depression symptoms, according to the National Institutes of Health.

What to do: Melatonin can help when used short term for such problems as jet lag. It is not particularly effective as a long-term solution for other causes of insomnia.


St. John’s wort is probably the most studied herb for treating depression. Researchers who analyzed data from 29 international studies recently concluded that St. John’s wort was as effective as prescription antidepressants for treating minor to moderate depression.

St. John’s wort appears to be safe, particularly when it’s used under the supervision of a physician.  However, it can cause unwanted mental changes.

Effects on the brain: St. John’s wort may increase brain levels of “feel good” neurotransmitters, including serotonin and dopamine. But unwanted mental changes that may occur in anyone taking St. John’s wort include anxiety, irritability and vivid dreams. It may also lead to mania (a condition characterized by periods of overactivity, excessive excitement and lack of inhibitions)—especially in individuals who are also using antipsychotic drugs.

Caution: This supplement should never be combined with a prescription selective serotonin reuptake inhibitor (SSRI) antidepressant, such as sertraline (Zoloft) or paroxetine (Paxil). Taking St. John’s wort with an SSRI can cause serotonin syndrome, excessive brain levels of serotonin that can increase body temperature, heart rate and blood pressure—conditions that are all potentially fatal. It also can interact with certain drugs such as oral contraceptives and immunosuppressant medications.

What to do: If you have depression, do not self-medicate with St. John’s wort. Always talk to your doctor first if you are interested in trying this supplement.


Older men whose testosterone levels are declining (as is normal with aging) are often tempted to get a prescription for supplemental “T,” which is advertised (but not proven) to improve their ability to get erections. Some women also use testosterone patches or gels (in much lower doses than men) to increase sexual desire and arousal.

Effects on the brain: If your testosterone is low, taking supplemental doses may cause a pleasant—but slight—increase in energy. However, with very high doses, such as those taken by bodybuilders, side effects may include aggression and mood swings. Men and women may experience withdrawal symptoms—such as depression and loss of appetite—when they stop taking it.

Testosterone replacement for men is FDA approved only for those with a clinical deficiency—defined as blood levels under 300 nanograms per deciliter (ng/dL).

What to do: Testosterone has been shown to increase sexual desire in women—it is not FDA approved for women but may be prescribed “off-label.” The evidence supporting testosterone’s ability to improve sexual function and well-being in normally aging men is weaker—unless they have been proven on more than one occasion to have low testosterone and related symptoms. Both men and women should take testosterone only under the supervision of a doctor.


Two ingredients that are commonly used in weight-loss supplements, beta-phenylethylamine (PEA) and ­P-synephrine, are said to increase energy and metabolism and burn extra calories.

Effects on the brain: Both PEA and P-synephrine (a compound found in supplements made from bitter orange) can make you feel jittery and anxious, particularly when they are combined with stimulants such as caffeine.

Many weight-loss and “energy” products are complicated cocktails of active ingredients that haven’t been adequately studied—nor have they been approved by the FDA. They’re risky because they’ve been linked to dangerous increases in blood pressure.

Important: There is little evidence that any of these products is particularly effective as a weight-
loss aid.

What to do: Don’t rely on weight-loss supplements. To lose weight, you need to decrease your food intake and increase your exercise levels—no supplement can accomplish that! 

Next month: Medications that can cause depression.