The likely cannot separate you this way.
AR 635-200, Paragraph 14–17, g., states that in cases where a separation for misconduct is recommended by an administrative board, disposition through medical channels is required if the “Soldier has an incapacitating physical or mental illness that was the direct or substantial contributing cause of the conduct, and action under the UCMJ is not initiated. A copy of the signed decision by the GCMCA will be included with the records.”
Are they giving you an administrative separation board? Is your Narrative Summary complete? Is your Dissociative state established by medical opinion/treatment notes during the same time period as your drug use? How many years do you have in and what is your grade?