For Stage 1, the study will last 14 weeks (about three and a half months). All study participants will have six (6) hour-long psychotherapy sessions and two (2) MDMA-assisted psychotherapy sessions lasting six to eight hours and requiring an overnight stay at the treatment facilities. The ordinary and MDMA-assisted sessions will be conducted by the same therapists. For the four subjects continuing into Stage 2, the study will last an additional 10 weeks (about two and a half months) with additional six (6) hour-long psychotherapy sessions and two (2) MDMA-assisted psychotherapy sessions lasting six to eight hours and requiring an overnight stay at the treatment facilities.