Gender does matter in clinical research

Excerpt

In 2013, the leading cause of Disability-Adjusted Life Years (DALYs) for ages 10–24 in both sexes was mental health disorders and substance misuse. However, during adolescence, depressive disorders were the leading cause for females (15–24 years), whereas road injuries were the leading cause for males of the same age. Sexual abuse was also a higher cause of DALYs for women than for men [5]. Additionally, prevalence, age of onset, clinical symptoms or outcome of many neuropsychiatric diseases substantially differs according to gender. Sexual chromosomes and sexual hormones may play an important role long before the age of puberty and especially during brain development. The organization of sexually differentiated brain circuits is based on many factors including sexual hormones, locally synthetized estradiol, androgens, genes located in the sex chromosomes including Sry and many others, as well as epigenetic mechanisms occurring at the DNA level. Neurosteroids may also influence DNA methylation and epigenetics. Examples of male-biased conditions mainly include early onset neurodevelopmental disorders such as autistic spectrum disorders, attention deficit hyperactivity disorders, language impairments or even schizophrenia; whereas examples of female-biased conditions rather include emotional disorders such as anxiety, depressive or stress and trauma-related disorders or even anorexia nervosa, which usually starts during puberty or later in life. In addition to sex differences in brain neuroanatomy and circuits, sex-specific variance was identified in various biological functions which may also result in sex differences in neuropsychiatric disorders [4, 7]. Finally, men and women are not equally exposed to psychosocial stressors, such as violence among many others during lifetime [2]. How much of the differences are due to biology and how much are the consequence of behavioral and sociological factors remains to be sorted out. …