---

This research is based upon reasonable evidence that the environment moderates behavioural effects of biological systems (serotonergic neurotransmission) involved in the development of juvenile affective symptoms. The data suggest that the Serotonin Transporter gene is a genetic substrate for youth internalizing behaviour: adolescents who carry a less functioning variant of this gene have a greater risk to develop depressive symptoms when exposed to environmental adversities. This gene also plays an important role in determining the continuity/discontinuity of depressive traits throughout adolescence, thus confirming the theory that carriers of the less efficient allele have more negative feelings (about themselves and the world), which could turn into depression when under stress. Primary prevention strategies, promoting proactive and adaptive coping behaviours may reduce the likelihood of persistence of behavioural problems from early- to late-adolescence and, perhaps, to early adult years.

---

Giampaolo Perna (M.D., Ph.D.) was the Vice Chief of the Anxiety Disorders Clinical and Research Unit and of the Psychiatric Day Hospital at the San Raffaele Hospital. From September 2009, he is the Scientific Director and Chief of the Department of Clinical Neurosciences at San Benedetto Menni Hospital of the Sisters Hospitallers.

Maria Nobile, MD, PhD, is Clinical Research Consultant at the Child Psychiatry Department of the E Medea Scientific Institute, Italy. She was in charge of several researches supported by the Italian Ministry of Health, on the role of environmental pathogens and candidate genes in child and adolescent psychopathology.

---