Final answer:
Functional family therapy is effective for adolescent at-risk behavior, and the functionalist theory emphasizes the regulation of sexual behavior to maintain family stability and cohesion.
Step-by-step explanation:
Functional family therapy, a therapeutic approach directed toward families, has proven effective in dealing with adolescent at-risk behavior. It is not primarily used for psychotic behavior, marital conflict, or sexual problems. When examining theoretical perspectives relating to family stability and marital cohesion, it is the functionalist perspective that stresses the importance of regulating sexual behavior. Functionalists view the family as the central unit of society and advocate for structures that support its preservation, especially in relation to sexual norms and behaviors which can impact family dynamics.