Re: Does a person't mind set alter correspondingly to a 24-hour cycle?

I am not sure what you mean by mindset in your question but if you mean 
ability to concentrate it is certainly true that we go through cycles in 
which we are sleepier and at other times we are more alert. Some people are 
clearly "morning people" and are able to get their best work done in the 
morning while others are able to do work at night. If you are thinking 
about mood, this is also dependent to some extent on time of day but more 
so on how much sleep we have gotten. Circadian clocks control many 
rhythms in your body and are primarily by the day:night cycle. These 
"clocks" cause a reduction in cortisol production and temperature and an 
increase in production of growth hormone and melatonin during the night 
hours (from fellow madscientist Sue Semple-Rowland, Ph.D.)  Melatonin has 
been shown to be somewhat useful in improving mood in Alzheimer's patients 
who were depressed and had sleep problems (Journal of Pineal research 
1998,25pp177-183). Also steroids (such as cortisol) are well known to 
affect mood and either cause depression or even psychosis in large 
amounts. Thus since our bodies do follow a circadian clock and different 
neuroactive hormones are released at different amounts during the day, it 
is likely that our brain activity and moods do cycle throughout the day.
hope this helps
cheers,
gabriel vargas md/phd