Increased risk of developing a sexually transmitted infection.
Explanation:
Combining drug abuse and unprotected sex with different partners can increase the risk of developing a sexually transmitted infection. This is because the practice of unprotected sex, ie without the use of condoms, is the most common way to contract a sexually transmitted infection. In addition, drug abuse is often done with injecting drugs, where users use the same needle and can pass infections on to each other.
Mental illness itself occurs from the interaction of multiple genes and other factors -- such as stress, abuse, or a traumatic event -- which can influence, or trigger, an illness in a person who has an inherited susceptibility to it.
