Antidepressants for people who don't have depression?

I receive several emails from people who are hesitant to take their prescribed medication after reading the package insert. In many cases, the reason is that they notice words such as “epilepsy” or “depression” in the recommendations for the medication. Why do doctors prescribe antidepressants for people who suffer from anxiety, anti-epileptics for those who suffer from chronic pain, or antipsychotics for those who suffer from mania, not schizophrenia?

The short answer is: because the brain functions with a surprisingly small number of substances that modulate neuron activity, and therefore there are few ways for the brain to go haywire—and few ways to intervene when it does. For this reason, the number of drug classes is quite small, and they end up being categorized according to their most well-known use.

If the problem is related to excessive neuron excitation, such as anxiety but also epilepsy, the treatment is to increase the brain's natural brakes by inhibiting neurons. The same substances that do this are therefore anxiolytic... and also antiepileptic. They also combat chronic pain when it is related to excessive brain activity.

If the problem is excessive dopaminergic modulation, which promotes both the personal salience of events (and therefore paranoia) and the degree of pleasure and motivation (and therefore mania), the solution is to reduce the action of dopamine. These substances are known as antipsychotics—but they also control mania.

If the problem is, on the contrary, a lack of dopamine modulation, one of the possible causes of the lack of pleasure and motivation associated with depression, the safest way to correct the problem is not to increase dopamine (since drugs that do this easily lead to addiction), but rather to use substances that cause the brain to increase its internal brakes. These are called antidepressants—and they also treat anxiety.

The names are sometimes scary, I know. But a little knowledge about your own brain solves the problem.

Excerpt from Suzana Herculano-Houzel (2025) Neuroscience of Everyday Life, originally published in Folha de São Paulo in August 2018