What category includes medications that treat seizures, anxiety, and insomnia?

Benzodiazepines are a class of medications that are specifically effective in treating conditions such as seizures, anxiety, and insomnia. They work by enhancing the effect of the neurotransmitter gamma-aminobutyric acid (GABA) in the brain, leading to a calming effect that helps manage anxiety and facilitates sleep.

Antidepressants, although used for mood disorders, do not primarily target the symptoms of seizures or insomnia directly; their action is more focused on improving mood and reducing the symptoms of depression. Opioids are primarily used to manage pain and do not generally have properties that treat anxiety or insomnia and can even cause respiratory depression. Antihistamines are primarily used for allergy relief and may have sedative effects, but they are not primarily used to treat seizures or anxiety disorders.

Thus, benzodiazepines stand out as the correct choice due to their therapeutic uses across all the mentioned conditions.