Which of the following can cause serotonin syndrome?

Serotonin syndrome is a potentially life-threatening condition resulting from an excessive accumulation of serotonin in the central nervous system. The primary cause of this condition is the use of serotonergic medications, especially when their doses are increased. Medications that increase serotonin levels include various antidepressants (such as SSRIs, SNRIs, and certain MAOIs), as well as other drugs like some pain medications and illicit substances.

When the doses of these serotonergic medications are raised, there is a heightened risk for serotonin to accumulate, leading to symptoms such as agitation, confusion, rapid heart rate, dilated pupils, muscle rigidity, and even severe complications like seizures or hyperthermia. Thus, increasing doses of serotonergic medications is a direct way to elevate serotonin levels in the body and can precipitate serotonin syndrome.

The other options do not have a direct connection to causing serotonin syndrome. For instance, regular exercise can actually be beneficial for mental health and does not affect serotonin levels in a way that would contribute to this syndrome. Similarly, a low-protein diet or vitamin supplementation is generally unrelated to serotonin levels; they do not contribute to the excess serotonin that characterizes serotonin syndrome.