Weaning off Lamotrigine after 5 years on AEDs

My son is 22 and weaning off 200 mg daily of Lamotrigine XR. He had one seizure about 5 years ago, unknown cause, and no other seizures. He has been on lamotrigine for 4 years, after about 8 months on the the first med they tried, Keppra. (He had terrible depression on Keppra, it was a nightmare). He is going down in dose by 50 mg every 2-3 weeks. He says he is OK but his mood is very agitated and somewhat irrational at times. Has anyone else experienced this type of mood swing/agitation while weaning off lamotrigine? How long do the withdrawals symptoms last, and anything we can do to make it easier? His neurologist is an epilepsy specialist who is well respected at a top hospital. He feels going down 50 mg every few weeks is safe and should not cause problems. But I think I am seeing some very worrisome signs of withdrawal from this med. Thanks for any input / advice!