I hadnt heard of the drug problems before, but it makes sense. So sad!
Harry and others who take drugs have had their minds altered and would like to let it be known that it's "everyone else's fault" but actually your family is only a small part that influences your behaviour:
Behaviour is affected by factors relating to the person, including:
physical factors - age, health, illness, pain, influence of a substance or medication (drugs of choice!)
personal and emotional factors - personality, beliefs, expectations, emotions, mental health
life experiences - family, culture, friends, life events
what the person needs and wants.
Behaviour is also affected by the context, including:
what is happening at the time
the environment - heat, light, noise, privacy
the response of other people, which is affected by their own physical factors, personal and emotional factors, life experiences, wants and needs.
So complicated!