Does my boss suffer bipolar disorder ?

He can be a downright monster at times.

He goes through very strange periods that have distinct patterns and depending on where he is on the cycle will determine how pleasant it is to work with him.

I know that he has a mental illness because he is seeing a therapist after he suddenly disappeared from the office for 3 months entirely unannounced. That came after a period of heightened intensity in his behaviour and paranoia and after he was making my life hell with overt office politics.

He seems to have two of three different phases. He seems to have characteristics that always co-exist in each stage. In one stage which I label the 'fun and relaxed' stage, he is lazy, doesn't care about the work as much and gets preoccupied with sex. He is more pleasant to work around when he is in that stage. He shows up to work late and leaves early.

In the 'monster' stage he is intense and driven by work and comes in early and leaves late taking on workaholic type of characteristics. He also becomes difficult and obsessive and plays office politic games to try and shore up his security of job in the office. He is sometimes unbearable when in this phase.

Some of us believe he suffers bipolar but frankly, none of us really understand the disorder. I am more studied in the personality disorders and can spot them a mile away which is why I believe my boss suffers NPD.

I guess the point of this post is to ask if it is likely he suffers bipolar disorder and to get any helpful tips on managing a working relationship with a sufferer.