Adolescence represents a period of many physical and neurological changes. It is also a period marked by an increased need to regulate emotions and behaviour in relation to long-term goals and consequences, often at a distance from the adults who provided regulatory structure and guidance during childhood.
The idea that adolescence is a heightened period of vulnerability specifically because of gaps between emotion, cognition and behaviour has important implications for our understanding of many aspects of both typical and atypical development during this period of the life-span.
In typical development, this framework is useful in helping us understand age-related differences in risk-taking and sensation-seeking (Steinberg, 2004). In atypical development, it helps us to understand why adolescence can be a time of increased risk for the onset of a wide range of emotional and behavioural problems, including depression, violent delinquency and substance abuse (Cicchetti & Cohen, 2006).
Watch Frances E. Jensen, MD, senior assistant in Neurology at Children's Hospital, Boston and a professor at Harvard Medical School talk about the most up-to-date research on the teen brain:
The Teenage Brain: part 1
Risk-taking behaviour or substance abuse during adolescence has both social and physiological consequences. For example, there is some evidence to suggest that nicotine is more neurotoxic in the adolescent brain compared to adults (Abreu Villaça et al., 2003). There is also evidence to suggest that adolescents that use cannabis before the age of 17 are more likely to exhibit poorer cognitive performance than late-onset users (over 17 years of age), especially in verbal IQ (Pope et al., 2003).
One reason why the consequences of emotion, cognition and behaviour in adolescence are so critical is due to parts of the adolescent brain structure still developing throughout this period and beyond. One of the most notable changes is in the balance between grey matter and white matter. Even relatively simple structural measures, such as the ratio of white to grey matter in the brain, demonstrate large-scale changes into the late adolescent years (Giedd et al., 1999). This continued maturation of emotional, intellectual and behavioural development has yet to be thoroughly investigated, but there is growing evidence that the second decade of life is a period of great activity with respect to changes in brain structure and function, especially in regions and systems associated with response inhibition, the magnitude of risk and reward, and emotion regulation.
Contrary to previous beliefs about brain maturation in adolescence, this activity is not limited to the early adolescent period, nor is it invariably linked to processes of pubertal maturation (see Figure 1). It is now clear from a number of studies that the human brain continues to change throughout adolescence (Blakemore & Choudhury, 2006).
It has been suggested that the impact of puberty on arousal and motivation occurs before the maturation of the frontal lobes is complete. This gap may create a period of heightened vulnerability to problems in the regulation of emotionand behaviour, which might help to explain the increased potential in adolescence for risk-taking, recklessness, and the onset of emotional and behavioural problems.