Summarize the following text. Many adolescents face pressure to use alcohol, cigarettes, or other drugs and to initiate sexual relationships putting themselves at high risk for intentional and unintentłonal injuries, unintended pregnancies, and sexually transmitted infections (STIs), including the human immunodeficiency virus (HIV). Many also experience a wide range of adjustment and mental health problems. Behaviour patterns that are established during this period such as the use or avoidance of drugs and taking or abstaining from sexual risk can have long-lasting negative and positive effects on future health and well-being. As a result, adults have unique opportunities to influence adolescents. Adolescents are different both from young children and adults. Specifically, adolescents are not fully capable of understanding complex concepts, or the relationship between behaviour and consequences, or the degree of control they have or can have over health decision-making, including that related to sexual behaviour. This inability may make them particularly vulnerable to sexual exploitation and high-risk behaviours. Laws, customs, and practices may also affect adolescents differently than adults. For example, laws and policies often restrict adolescents' access to reproductive health information and services, especially when they are unmarried. In addition, even when services do exist, provider attitudes about adolescents often pose a significant barrier to the use of those services.