Well first of all it is wrong to diagnose a person with both Bipolar disorder
at the same time since both these conditions are mutually exclusive of each other. However a positive thing in providing treatment for both of these conditions is that an anti psychotic medication
works very effectively in both the conditions by lowering the dopamine levels in the brain since excessive dopamine levels in the brain have been considered to have been associated with either of these conditions. So practically speaking use of an anti psychotic drug shall help your client irrespective if he is schizophrenia or bipolar disorder but more importantly i will urge you to get a revision of your diagnosis of the patient since first he is too young to have a diagnosis such as these and secondly the diagnosis is not correct since both these conditions cannot be labelled in the person simultaneously.
Role of norepinephrine
and serotonin is limited in such a patient, drugs which may increase their levels in the brain may help in treating depression ( if the person is bipolar disorder) or negative symptoms ( if the person is schizophrenic).
I hope this helps.