Among therapy professionals, psychologists undergo the longest and most extensive training in the provision of mental health services. This includes 4 to 5 years of graduate study and research in psychology/psychotherapy, followed by an intensive year-long internship, often in a hospital or clinic setting. Additionally, many psychologists go on to complete a 1 to 2 year postdoctoral fellowship in an area of specialty after graduation. Given the rigorous training required to earn a doctoral degree (Ph.D. or Psy.D.), psychologists frequently have significant experience working with a wide-range of problems and have a deep knowledge of clinical research, theory, and techniques.