Researchers at UCL, UK found that young people who were happier and more aware of the harms of alcohol and cigarettes were more likely to never drink or smoke than those who were less aware or perceived themselves as less happy.

The research team found that nearly 70% of the study participants labeled themselves as persistent non-users of alcohol and cigarettes, and around 13% categorized themselves as persistent users. Those that defined themselves as persistent non-users scored highest on harm awareness and happiness tests compared to the rest of the groups.

Dr Noriko Cable, the corresponding author at UCL Institute of Epidemiology & Health said: "We were surprised to find that while knowledge of alcohol and smoking related harm for most young people was associated with them never drinking or smoking, for some adolescents harm awareness seemed to be associated with them picking up drinking or smoking. It is possible that positive expectations from drinking alcohol or smoking cigarettes may have overcome some young people's awareness of harm from using those substances. Having supportive friends did not protect adolescents from using alcohol or cigarettes."

To examine whether happiness, awareness of alcohol- or smoking-related harm or the size of friendship networks were associated with young people's drinking and smoking behavior over time, the authors used data on 1,729 adolescents (849 boys and 869 girls) aged 10 to 15 years who submitted data at two time points for the UK Longitudinal Household Study. The study has been collecting data representative of the UK population from 40,000 households every year since 2009.

Combining young people's responses from the two time points, the researchers created four categories of alcohol and cigarette use: persistent non-use - not using alcohol or cigarettes at both time points; ex-use - using alcohol or cigarettes when first asked but not at follow up a year later; initiation - non-use at first time point, but use of alcohol or cigarettes at follow up; and persistent use - use of alcohol or cigarettes when asked at both time points.

About 8% of the study group labeled themselves as ex-users and about 13% had started using alcohol or cigarettes between the first time point and follow-up a year later (initiation). Young people aged 10 to 12 years were more likely to be in the persistent non-use group, whereas participants aged 13 years and over were more likely to be in the persistent user and initiation groups.

Happiness was assessed in six areas of young people's lives: school performance, looks, family, friends, school and life in general. Participants were asked to rank these areas of their lives on a scale from one (very happy) to seven (unhappy). Young people were also asked how harmful they thought various types of alcohol and cigarette use, for example occasional smoking, daily smoking, or heavy weekend drinking, were on a scale from one (no risk) to four (great risk).

This was an observational study so it can increase our understanding of young people's drinking and smoking behavior but it cannot show cause and effect because other factors may play a role. Dr Cable also commented that: "Because the information used in this study is self-reported, the findings should be interpreted with caution, but they do suggest that making adolescents aware of alcohol and smoking related harm can be helpful in preventing them from engaging in risky health behaviors."