The following excerpt is taken from a report from Ireland with an important conclusion about the importance of one good adult relationship in young people's lives and it's importance for mental health development.  The complete survey can be found at http://www.headstrong.ie/content/myworld

Emerging patterns across a young person’s life 
The developmental data provided by the MWS allow us to see, for the first time, the mental health difficulties that young people experience across this vulnerable time span in their lives. 

• We see an increase in young people’s levels of depression, anxiety and stress across the developmental period of 12-25 years. 
• We see a steady increase in levels of alcohol consumption, frequency and volume of drinking, number of alcoholic drinks typically consumed, and binge drinking across the 12-25 age group. Young people move outside the normal range for drinking at 18 and remain outside until about 24-25. 
• Avoidant coping, a negative coping strategy, peaks at 20-21 years, then declines towards age 24. 
• At 18-19 years, young people report a high level of substance use, which continues until they are 24-25. 
• Levels of both self-esteem and optimism generally decrease from 12-18 years, whereby at 18-19 both are at their lowest. Levels increase gradually from about 19 onwards. 
• A positive coping strategy (that is, the use of problem-focused coping) is at its lowest at 14-15 years, and gradually increases up to 24-25. Levels of seeking social support are highest at 12-13, drop at 18-19 and remain at this level up to 25. 

It is evident from our findings that mental health difficulties emerge in early adolescence and peak in the late teens and early 20s. This peak in mental health difficulties, in general, is coupled with a decrease in protective factors such as self-esteem, optimism and positive coping strategies. The evidence indicates that this stage of a young person’s life is a particularly vulnerable period. This profile of the emergence of mental health difficulties highlights the importance of early intervention. 

Dooley, B. & Fitzgerald, A. (2012) 'Methodology on the My World Survey (MWS): a unique window into the world of adolescents in Ireland'. Early Intervention in Psychiatry, doi: 10.1111/j.1751-7893.2012.00386.x. [Epub ahead of print].