Final answer:
Major depressive disorder is the most common psychological disorder among the options given, with a lifetime prevalence of around 15-20%, compared to other disorders like OCD, panic disorder, and dissociative identity disorder.
Step-by-step explanation:
The psychological disorder that is most common among the options provided is major depressive disorder (MDD). This mood disorder can be characterized by intense feelings of sadness and despair, significant weight loss or gain, decreased libido, and disruption of hormonal circadian rhythms, among other symptoms. MDD is not just about feeling sad or blue, it is a long-term condition that can greatly impair an individual's ability to function on a day-to-day basis and may require treatment. According to research, the lifetime prevalence estimate is around 15-20%, making MDD one of the most common mental disorders, as opposed to disorders such as obsessive-compulsive disorder (OCD), panic disorder, and dissociative identity disorder which are less prevalent.