Sexual behaviour

Discussion of sexual lifestyle and the ability to take a sexual history are relevant to many types of clinical practice. The age at which people first have sex has decreased and the age at which people start cohabiting has become later in recent decades, increasing the time available to accumulate sexual partners and thus be at risk of sexually transmitted infections (STIs), including human immunodeficiency virus (HIV). While many people have few partners, a small proportion of the population has many. People with many partners are most at risk of STIs, but there are many other influences including the gender, age, and ethnicity of their partners and the type of sexual practice. This chapter covers the adverse consequences of sexual behaviour (including STIs and unintended pregnancy), and initiatives to encourage reducing partner numbers, using condoms and effective contraception, and engaging in less risky practices.