Why do many psychiatric disorders emerge during adolescence? 

Adolescence is a critical developmental time period marked by the increased incidence of a myriad of psychiatric illnesses, including but not limited to: anxiety and mood disorders, eating disorders, substance abuse disorders and psychosis. It is believed that abnormalities in maturational events that typically accompany adolescence may contribute to psychopathologies. 

Areas of research that study the effect of aberrant brain and neural development typically focus on studying and understanding: 

• Trajectories of grey/white matter volume and cortical thickness: MRI evidence suggests that cortical grey matter and cortical thickness decrease during adolescence, which has commonly been interpreted as being the result of synaptic pruning, a process by which redundant (and therefore unnecessary) synapses are eliminated through an experience-dependent process throughout early development. However, these decreases in volume/thickness do not apply to all brain areas, as some display a nonlinear relationship with age. Volumes of white matter usually show a linear increase throughout childhood and adolescence.
• Changes in myelination and synaptic pruning and their effect in the formation of functionally interconnected circuits: This is one of the most popular areas of study, as changes in synaptic pruning and myelination have been the most popular explanations for the structural differences in the adolescent brain. Early post-mortem studies have indicated a decrease in the number of synapses during childhood and adolescence. Newer evidence, however, has indicated that the gradual decrease of synapse number begins in childhood (in several cortical regions) and continues through adolescence. 
• Changes in brain activity of neural networks: Age-related changes in neural connectivity and neurotransmission are thought to underlie the functional changes associated with adolescence.Using fMRI techniques, researches have found that adolescents show differential functional connectivity across multiple circuits. Some of these include: the action-observation network, considered by many to be the neural substrate of imitation; the biological-motion processing network, also known as the superior temporal sulcus (STS) network, implicated in the extraction and encoding of socially relevant cues imparted by movement (i.e. eyes, hands, etc); and, the executive network, which underlies multiple cognitive processes involved in decision-making and working memory.Adolescents have also long been regarded as being high risk takers and displaying increased novelty-seeking behaviors.
• Neurochemistry: Finally, the efficacy of communication and integration of neural networks depends on neurotransmission and the state of these transmitter systems. Due to the experimental constraints of studying human children and adolescents, the scientific knowledge of developmental changes in neurotransmitter systems is limited. Most of the known data comes from post-mortem or nonhuman primate studies. However, one of the better studied systems is the developmental changes in dopamine neurotransmission and its relation to adolescent-specific changes in motivational behavior. The mesolimbic dopamine pathway, a key circuit implicated in reward and addiction, has been found to be anatomically and functionally distinct in adolescents. 

After reading all of this, one thing is clear: there is no single answer. Adolescence is the product of many integrated developmental and functional changes. Both our body and our brains are constantly changing to reflect what we’ve learned and what is necessary for survival. Additionally, many other factors come into play in influencing healthy and normal development like sleep patterns, history of disease, hormonal changes underlying puberty, dietary habits and teenage smoking/drinking. 

Makes you feel like going back in time and taking better care of yourself as a teen doesn’t it?