Garrett’s family is worried about his behavior. He no longer displays affection toward family members, refuses to bathe, and thinks that his neighbor’s dog is sending him coded messages in his cereal. Garrett’s family takes him to a mental health practitioner, who is most likely to treat him with

"Antipsychotic medication" would be the right solution.

Explanation:

Antipsychotics are becoming a class of chemical compounds probably largely required to fully treat medical conditions of psychological disorders, including certain schizoaffective disorder, as well as mania, occasioned induced bipolar disorder. Often, they could be used to combat extreme depression as well as serious anxiety. Antipsychotics are often referred to as big tranquilizers.