This chapter discusses the neuropsychiatric disorders due to drugs or medical illness. This chapter covers the medical conditions associated with psychiatric symptoms, drug-induced psychotic disorders, body weight disorders, and appetite stimulants. Weight gain is often associated with psychotropic drug therapy specially antidepressants, antipsychotics or mood stabilizers. It may also be associated with binge eating disorders. Obesity is defined as body mass index (BMI) greater than 30 kg/m2. Medications approved for weight loss acts either by decrease in appetite, increase in satiety or decrease in GI absorption.