Psychiatry
Freud, among others, argued that neither predominantly different- nor same-sex sexuality were the norm, instead that what is called "bisexuality" is the normal human condition thwarted by society. A 1901 medical dictionary lists heterosexuality as "perverted" different-sex attraction, while by the 1960s its use in all forums referred to "normal" different-sex sexuality.
In 1948 Alfred Kinsey publishes Sexual Behavior in the Human Male, popularly known as the Kinsey Reports.
Homosexuality was deemed to be a psychiatric disorder for many years, although the studies this theory was based on were later determined to be flawed. In 1973 homosexuality was declassified as a mental illness in the United Kingdom. In 1986 all references to homosexuality as a psychiatric disorder were removed from the Diagnostic and Statistical Manual of Mental Disorders (DSM) of the American Psychiatric Association.
Read more about this topic: History Of Homosexuality