Toxoplasmosis is a worldwide disease caused by Toxoplasma gondii which is an obligate
intracellular parasite that affects warm-blooded mammals including man. T. gondii neurotropic
nature made it a potential causative agent for psychiatric and behavioral disorders. T.
gondii uses a complicated mechanism to gain access to the brain, where it invades different
brain cells, including astrocytes and neurons forming cysts. Attention deficit hyperactivity
disorder (ADHD) represents a neuropsychiatric alarm-ing concern due to its indefinite etiopathogenesis
among children. Depression as major depressive disorder (MDD) is a common
and serious psychiatric illness that negatively affects feeling, thinking and acting. Owing to
the high prevalence of toxoplasmosis and the increased incidence of ADHD and MDD in recent
years, this review studied the relationship between toxoplasmosis and each of ADHD and
MDD.