Mentally handicapped isn't a specific medical condition. He does have mental handicaps in that he has no concentration, he's a narcissist, etc.

How much of his mental and emotional deficiencies are a result of choices he made is really impossible to determine. I've heard people say he has behaved the same way his whole life, so maybe it wasn't a choice.

He is clearly mentally and emotionally stunted in many ways though. I didn't mean to say he has down syndrome or any other specific mental handicap but was using mental handicap in a broad sense. And I wasn't intending it to be strictly an insult but rather a statement of fact, he is mentally deficient/stunted/handicapped in a number of ways.

He's not a normal adult.