thanks for using health care magic.
remeron containing mirtazepine is good anti depressant
drug. but it can cause increase sleep and weight gain.
I think he still does not have much improvement in his depression and hence he has all the symptoms.
You should consult his psychiatrist
for line of managment. he may be benefitted with fluoxetine or sertrailne or des venlafaxine
He should also check physical causes like thyroid dysfunction
or vitamine B12 deficiency.
Counselling may be of some help as well.