What causes derealization and depersonalization?

Many conditions : Depersonalization and derealization can be because of panic disorder. There's a condition called primary depersonalization disorder as well. Temporal lobe epilepsy can also cause these conditions. Any of dissociative disorders can certainly have derealization and depersonalization is a component. We do not know the underlying physiology of this condition however. Certain hallucinogens such as lsd, pcp, and certain mushrooms, have also been known to cause both of these conditions as has high-dose marijuana over a prolonged period of time. I have seen one case of Hydroxyzine overdose prolonged depersonalization. Withdrawal from certain substances of abuse can also cause depersonalization and derealization. It is not at all unusual for someone to experience derealization and occasional depersonalization as part of development through adolescence.