What is the underlying cause of schizophrenia and why does it typically emerge at age 20?

I would imagine its due to hormonal changes coupled with strong instincts which are too strong to handle at that age. It could also be due to stress and expected high life demands. I would imagine that its good to administer high doses of vitamins B complex in the growing years to calm the brain down and get the individual to think positive since the food we eat is devoid of many nutritional values. Plenty of vegetables and fruits - little meat and fish is best for a calm brain. Also understanding psychology and how the brain works should be a compulsory topic for all children so they can understand their perception.We need to teach children the value of "concentrating" (reading) on various topics of life rather than leaving the mind idle and weak and open to all sorts of mental problems.

I believe most schizophrenia is not inherited but a social problem.

Concentrating is good for the mind as it helps keep the division strong between the conscious and the subconsciousness of our minds

and

not the subconsciousness leaking into the our consciousness due to idleness.

Some lastly, on an emotional footnote, some children may have undergone some sort of trauma or pressure in the home.

Schizophrenia is mostly inherited disease and has to be controlled only by psychiatrist. It emerged up to 20 to 24 years in general.
My stepdaughter was diagnosed with schizo when she was 21.The Dr eventually figured out that the marijuana and huffing spray paint brought the disease on earlier than it would've normally appeared. In fact, schizo usually does not hit an adult until he or she is in their late 30s or early 40s. I don't know that there is a specific cause but heredity plays a big part.We were told that my sdaughter would've eventually gotten it, she chose to get it earlier than she needed to by using drugs.