Originally Posted by paddy

I wonder whether your Dad is actually depressed or just suffering from the lack of motivation which as mentioned above is a symptom of PD. In the run up to my diagnosis I could sit for en entire day apart from feeding myself and have no interest in doing anything whatsoever. I knew I wasn't sad/depressed but was inert and fortunately for me the next day I would be better - perhaps my brain needed a rest from the multi-tasking. I have been depressed in the past and it is very similar but once on the right meds. - sinemet with the addition of rasagiline 18 months later - I am quite the busy bee.
I keep my diary full so that if I do have the odd inert day I am drawn back into activity so if as Lindylanka suggest you can make suggestions and your Dad goes along with it, it will keep him going forward