Psychotropic medications and the developing brain

Increasing numbers of children and adolescents are treated with psychotropic medications for Major Depressive Disorder (MDD) or Attention-Deficit/Hyperactivity Disorder (ADHD). Although these psychotropic medications have been well studied in the adult population, much less is known on their long-term effects on human brain development. However, animal studies illustrated that these medications induce long lasting, possibly permanent, changes in specific systems and regions in the brain when prescribed at a younger age, i.e. when the brain is still developing; a phenomenon known as ‘chemical imprinting’. Here, we conducted a series of clinical studies to investigate whether chemical imprinting also occurs in the human brain. To this purpose, we investigated the age-dependency and long-term effects of both methylphenidate treatment for ADHD and antidepressant treatment for MDD.
The main results of this thesis indicate that also in the human brain the effects of ADHD medications are dependent on age. For instance, early-, but not late exposure to methylphenidate lastingly affected the GABA neurotransmitter system, but methylphenidate also had a lasting positive effect on sleep in children with ADHD. However, we could not replicate these chemical imprinting findings for antidepressants. The work described in this thesis contributes to a better understanding of the effects of psychotropic medications on the developing brain, and illustrates the need for more longitudinal follow-up studies into the long-term effects of psychotropic medications on the human brain.