The timely documentary Diagnosing Difference examines the medical community’s ongoing practice of treating people whose gender expression is different from their birth-assigned gender as mental patients suffering from a disorder.

Since 1980, the American Psychological Association (APA) has included “gender identity disorder (GID)” in its Diagnostic and Statistical Manual of Mental Disorders (DSM) — what some call the Bible of psychological treatment.

The DSM shapes how doctors treat those who identify on the trans spectrum (not all people who are gender variant identify as trans), and how gender is treated under the law and in social life.

With the APA set to introduce an update to the DSM in 2012 (only the second revision since 1980), pressure is mounting for the section on GID to be removed or heavily revised.

Some of the talking heads in Diagnosing Difference note that GID diagnosis is for now an unfortunate but necessary tool for them to access medical treatment and eventual legal recognition of their chosen gender. Others say the diagnosis — implying sickness — is stigmatizing — socially, culturally and legally.

One of the key threads of the hour-long doc is that there is no monolithic trans experience or community with clearly defined goals and needs. Each trans person needs to be treated as an individual with unique experiences and desires for their gender expression.

It’s a stunningly obvious conclusion that nonetheless bears repeating for how often it is lost on people obsessed with genital status and normative gender expression.

At one point, a trans person recalls how her doctors asked if she enjoyed playing with dolls and makeup as a child, rather than asking if she liked Joan Jett and long guitar solos. It’s a clear reminder that gender is performed and enjoyed in ways as numerous and different as the sum total of humanity, and that we can’t reduce people’s gender expressions to simple categories.