Given that foods and nutrients have been shown to influence the pharmacokinetics of drugs, drugs may cause changes in the nutritional status of patients and their response to a given drug. Food-drug interactions are particularly relevant for drugs used to treat neurological and psychological diseases. This review provides an overview of food-drug interaction in the treatment of neurological and psychological diseases. A literature search was carried out by collecting data from different reviews, reports, and original articles on general or specific drug interactions with food, in patients with a variety of neurological and psychological diseases. Based on our review, we found that food-drug interactions may alter the expected impact of drug, or cause the development of a drug toxicity. Nutritional status of the patients may also be affected, particularly a change in body weight caused by a change appetite. Metabolism, absorption, and excretion of foods may also be altered, and nutritional insufficiencies may occur. Recent studies show that diet can have a strong influence on gut microbiota and thus, alter drug pharmacokinetics. Therefore, microbiota alterations should also be considered while assessing food-drug interactions. Knowledge of food-drug interactions is critical for improving health of patients with neurological and psychological diseases, and also for improving effectiveness of treatments.