“In the last couple of decades, many medical institutions have moved away from the view that being transgender is the result of mental illness, as they previously did with homosexuality.” (http://time.com/4424589/being-transgender-is-not-a-mental-disorder-study/)
Transgender is a term for a person who was born in one sex but has a feeling they are the opposite gender. They often will go to lengths to transform their body to match the feelings they have. According to times, this used to be considered a mental disease but now it isn’t by most organizations. This seems to be done out of practical considerations for how transgender people are treated. Strictly speaking though, the move away from a mental disorder is a tricky one. According to psychiatry.org mental illnesses are ” are health conditions involving changes in thinking, emotion or behavior (or a combination of these)”. This definition rather lose. The definition covers every single person without further stipulation since everyone faces some changes in thinking, etc. (The National Alliance on Mental Illness define mental illness the same way). Clearly, a stipulation such as a frequent change that doesn’t normally occur in other people would be needed. This definition probably needs further clarification as well but should work for our purposes. Now, it seems clear that a transgender person faces a mental difference(s) that most people do not. Does this mean that gender dysphoria is automatically a mental illness? Not necessarily. A view that can help people who wish to claim gender dysphoria is not a mental illness is substance dualism (perhaps other dualism views could as well).
Substance dualism is the idea that people are more than their physical body. Typically there is a brain and a mind/soul. Under this view, a person could be born in the wrong body in the sense that their soul is the opposite gender from their biological sex. If that is the case, then the dysphoria would be a problem based on the incompatibility of the body/soul instead of a brain issue. Now, to be clear I am not making any claims about the truth values of gender dysphoria, substance dualism, or mental illnesses. Rather, I am making the claim that substance dualism would have to be true for gender dysphoria not to be a mental illness. However, it could be the case that substance dualism is true and gender dysphoria is a mental illness, but a different kind of argument would have to be made.