From Nonbinary Wiki

    The diagnosis of 'Transsexualism' was introduced in the Diagnostic and Statistical Manual of Mental Disorders (DSM-III) compiled by the American Psychiatric Association (APA) in 1980 for individuals who had experienced a minimum of two years of continuous interest in reconstructing their sex-physicality and assigned gendered identity. The criteria of the diagnosis focused on individuals whose identities resembled a male-to-female (MTF) or female-to-male (FTM) paradigm. Others experiencing gender dysphoria, but whose identities did not fit the MTF/FTM paradigms could be diagnosed with 'Adulthood Nontranssexual Type', or 'Gender Identity Disorder: Not Otherwise Specified' (GIDNOS). In 1994 the DSM-IV committee replaced the transsexual diagnosis; for individuals with MTF/FTM type identities a diagnosis of 'Gender Identity Disorder' (GID) would be applied instead. The diagnostic criteria of GIDNOS was left undefined, bar that the diagnosis be given to those whose 'gender identity disorder' cannot be defined within a MTF or FTM paradigm. Though a gender dysphoric nonbinary individual may use the term 'transsexual' to describe themselves, they are not considered to be transsexual within a clinical context.