A01

• What does DSM-5 specifically exclude in its categorization of gender dysphoria?

  Intersex conditions with a biological basis
• Why might gender dysphoria be subject to biological influence?

  It may have a basis in brain structure
• What is the bed nucleus of the stria terminalis (BST) associated with?

  Emotional responses and male sexual behavior
• How does the size of the BST differ between men and women?

  It is larger in men than in women
• What was found about the BST size in transgender females?

  It was found to be female-sized
• What does the BST size suggest about individuals with gender dysphoria?

  They have a BST size of their identified gender
• What do transgender individuals report feeling from early childhood?

  That they were born the wrong sex
• What did the follow-up study by Kruijver et al. (2000) find about transgender individuals?

  Average BST neuron number in the female range
• How many twin pairs did Frederick Coolidge et al. (2002) assess for gender dysphoria?

  157 twin pairs
• What percentage of variance in gender dysphoria did Coolidge et al. find could be accounted for by genetic factors?

  62%
• What does the finding of a strong heritable component in gender dysphoria suggest?

  Genetic factors play a significant role
• How many MZ twins were compared to DZ twins in the study by Gunter Heylens et al. (2012)?

  23 MZ twins and 21 DZ twins
• What was the concordance rate for gender dysphoria in MZ twins found by Heylens et al.?

  39%
• What does the finding that none of the DZ twins were concordant for gender dysphoria indicate?

  Genetic factors may influence gender dysphoria