The most prevalent psychiatric disorder in the u. s. is1) mood dysregulation disorder2) cyclothymia3) major depressive disorder4) bipolar disorder

3) Major depressive disorder  

Explanation: Major depressive disorder is basically a mood disorder that causes a persistent feeling of disinterest, dullness and sadness. It is a form of clinical depression which affects how patient feels and affects his/her way of thinking and behaving. It leads to a variety of emotional as well as physical problems affecting normal day-to-day activities. In extreme cases it makes patient feel as if life isn't worth living.