For some, however, these feelings are more serious, and they could indicate a mental or emotional problem. Clinical psychology is a broad branch of psychology that focuses on diagnosing and treating mental, emotional, and behavioral disorders.Some of the more common disorders that might be treated include learning disabilities, substance abuse, depression, anxiety, and eating disorders.or example, a clinical psychologist might focus on working with children or the elderly, or they might focus on working only with patients who are diagnosed with eating disorders or post-traumatic stress disorder. Simply put, a clinical psychologist has three main duties: 1.