<prompt> Most common psychiatric illness -DepressionBipolarManiaCyclothymia  <response>: Ans. is a i.e., Depressiono Depresson is the most common psychiatric disorder that affect 15 of the population at some time in their lives Mates - 8-12; Females -20-25. Middle aged 25-45 years females are most commonly affected.o Note : Among the given options, depression is most common. Overall, anxiety disorder is the most common psychiatric illness. 