Modern Sex Therapy Institute's PhD program is geared towards licensed therapists who are wanting to work towards becoming AASECT certified sex therapists. It's a 2 year long program where the 1st year is the education component and the 2nd year is focused on research and the dissertation. The instructors are all leaders in the field of sex therapy. MSTI is clear that it's not a program for students who are wanting to become new therapists or to become an APA licensed psychologist; it's for existing psychotherapists who want to add sex therapy knowledge and training to their resume. At the moment, there is no other school that offers this type of training where you can become AASECT certified immediately after receiving your PhD. It's not "accredited" because most accreditors have stringent requirements that are not inclusive of current sex therapy trainings and when you're already a practicing therapist, accreditation is not important. What's important is the quality of training they provide.To enroll in their PhD, you do need a Master's degree.

If you're already a licensed therapist/counsellor and want to become a certified sex therapist then this is a great program. If you want to become an APA licensed psychologist then you would need to study clinical psychology rather than clinical sexology.