Childhood and adolescence is a period of experimentation, sometimes linked to engagement in behaviours that are harmful for health, including tobacco consumption and the use of illicit drugs. Children and adolescents who smoke tobacco are more likely to become regular tobacco smokers in adulthood. Tobacco smoking in childhood and adolescence has both immediate and long-term health consequences, increasing the risks of respiratory diseases like asthma in the short term and the risks of cardiovascular diseases, respiratory illnesses and cancer in the long term.

Tobacco consumption is the largest avoidable behavioural risk factor to health in the European Union and the most significant cause of premature death across EU countries, accounting for about 700 000 deaths per year. Around half of smokers die prematurely, dying 14 years earlier on average (European Commission, 2020). It is a major risk factor for at least two of the leading causes of mortality – circulatory diseases and cancer – and an important risk factor for many severe chronic respiratory diseases.

Alcohol use in adolescence continues to be very common in Europe with two in three adolescents aged 15 years old having tried alcohol at least once in their life in 2018, although the proportion of adolescents reporting to have been drunk more than once in their life has decreased in recent years ().

Alcohol-related harm is a major public health issue in the European Union. Alcohol use is responsible for some 255 000 to 290 000 deaths each year across EU countries (WHO, 2019; IHME, 2019). High alcohol consumption is associated with increased risk of heart diseases and stroke, liver cirrhosis, certain cancers and foetal alcohol disorders, but even moderate alcohol consumption increases the long-term risk of developing such diseases. Alcohol also contributes to morbidity and mortality through accidents and injuries, violence, homicide and suicide.

The use of illicit drugs remains an important public health issue in Europe. Almost a third of adults in the European Union aged 15‑64, or around 97 million people, have used illicit drugs at some point in their lives, with the experience of drug use being more frequently reported by men than women. Cannabis is the most frequently used drug, but some have also used cocaine, ecstasy (MDMA), amphetamines, and other drugs (EMCDDA, 2020). The use of illicit drugs, particularly among people who use them regularly and heavily, is associated with higher risks of cardiovascular diseases, mental health problems, accidents, as well as infectious diseases such as HIV when the drug is injected. Illicit drug use is a major cause of preventable mortality among young people in Europe, both directly through overdose and indirectly through drug-related diseases, accidents, violence and suicide.

Nutrition is fundamental for child and adolescent development and long-term health. Taking good nutrition habits at a young age, including eating fruit and vegetables regularly, can protect against many serious health problems such as obesity and diabetes.

Physical activity is beneficial for child and adolescent development and can set good habits for adulthood, thereby influencing health outcomes later in life. WHO recommends that children do at least 60 minutes of moderate-to-vigorous physical activity daily, yet these recommendations are not met by most children and adolescents in all countries.

Overweight and obesity among children and adolescents is a major public health issue. Children and adolescents who are overweight or obese are at a greater risk of poor health, and this effect persists into adulthood. Moreover, obesity among children and adolescents is often related to psychosocial problems such as poor self-esteem, bullying and underachievement at school, which can further worsen health and economic outcomes in adulthood (OECD, 2019).

Obesity is a known risk factor for numerous non-communicable diseases, including hypertension, diabetes, cardiovascular diseases, and some forms of cancer. On average in the EU, overweight and obesity reduce life expectancy by nearly three years (OECD, 2019). Evidence from some countries also suggests that obesity increases the risk of developing severe COVID‑19 symptoms and requiring intensive care (Caussy et al., 2020).