- Polymorphism of the serotonin-2A receptor gene (HTR2A) associated with childhood attention deficit hyperactivity disorder (ADHD) in adult women with seasonal affective disorder. Levitan, R.D., Masellis, M., Basile, V.S., Lam, R.W., Jain, U., Kaplan, A.S., Kennedy, S.H., Siegel, G., Walker, M.L., Vaccarino, F.J., Kennedy, J.L. Journal of affective disorders. (2002)