I suffer from insomnia when i know that someone has died. why?what's the cure?

Therapy?: Have you yet tried any form of psychotherapy? Typically, the optimal combination of things to treat emotional issues such as depression is medication (which, on your best day, is supposed to take the edge off symptoms) but the real gruntwork takes place in psychotherapist's consulting room.

Anxiety, distress: I am assuming that these are,people that,you know that have died. Death is an upsetting topic as it makes us,think about the loss,of significant others and/or our own mortality. There are no clear answers to the feelings that may come up and they are often not clearly formulated . Your insomnia may be an expression of,these feelings which are not in words. Counseling may,help give you clarity.

Grief: Agree with the earlier answers. Deep grief can effect us physically, emotionally and spiritually. Consider talking with a pastoral care provider or therapist.