Does this absolutely have to be more than two hours long? I'm thinking no. My impression is that Kazuhiro Soda, an enthusiastic and compassionate young documentary director from Tokyo, fell in love with his material, and I can see why. Some of the lives he has touched are sure to stay with you for quite a while. But I also think Soda could have achieved his goal of familiarizing us with the work of Dr. Masatomo Yamamoto, a psychiatrist with a heart of gold, in half the time. Having said that, I have to admit "Mental" is a fine sample of what you may call minimal invasion movie-making. The interference is limited to a few occasional questions and the obvious presence of camera and light. In effect, something real is revealed about Dr. Yamamoto, his patients, and contemporary Japan. Soda himself calls his approach "observational", and perhaps it works so well because it corresponds to Dr. Yamamoto's therapeutic technique. Generally a gruff guy, he does a lot of listening and works with simple diagrams scribbled on small pieces of paper, outlining the cycle of life and illustrating how a 'destination to go' and a 'place to be' can add up to a 'reason to live'. It's easy to see why, in his patients' eyes, Yamamoto is more god than man: "He is greater than Buddha."