Mental clarity, depression, low cholesterol

I am a 45 year old female with 2 college degrees.  I have always been an excellent student with a sharp memory.  In the past 10 years, I have experienced varying degrees of depression, anxiety, and concentration/mental clarity problems.  I am 5'5", 129 lbs., and run 15-20 miles per week. I take no medications.  I have irritable bowel and severe endometriosis.  2 years ago, during testing for my GI symptoms, I was told I had "sludge" and a polyp in my gall bladder.  After laparoscopic surgery (the polyp was not found) my GI symptoms resolved - for about 6 weeks.  Since that time, I have had difficulty eating foods high in fat.  In an effort to resolve related symptoms, my doctor prescribed Colestipol to absorb excess bile and fats.  Though my GI symptoms improved, I began a 6 week slide into my worst episode of depression.  In addition, I was anxious, lethargic, and had difficulty exercising.  My concentration was terrible, my focus nonexistant, and I embarrassed myself by forgetting words and names of people I know well.  After finding no side effects of the medication which would explain this, I wondered if I had become nutritionally deficient during its use, and stopped taking it.  The fog began to clear in the first week, and within 2-3 weeks I began feeling much better.  
A possible connection occured to me then: I have always had a low total cholesterol level, ranging from 103 to 124 in the times I have had it checked in the past 15 years.  My last result (2 years ago) showed TC of 119, trigylicerides 59, HDL 68, LDL 39.  Before the Colestipol I have never taken medication which lowers cholesterol.  My doctor agrees that I probably pushed my levels too low with the Colestipol, resulting in my symptoms, and does not feel like I need to act further.  Research I found indicated that "very low" cholesterol (defined as below 160) increased risks of depression, anxiety, concentration, word recall, hemorrhagic stroke, heart disease, and several types of cancer.  My doctor has stated that most people with cholesterol this low are malnourished, often due to alcholism (alcoholism), and I shouldn't worry since this is not true for me.  I am concerned about the frequent concentration problems I have had, which have affected me to the extent that I had to drop out of an online course I wanted to take, and the other mental symptoms (and possible health risks including effects on seretonin, hormones, etc.) as well.  Since I have trouble ingesting fat, do you feel this is a real concern?  To what extent do you feel that naturally occuring low cholesterol affects the brain?  What can I do so I can think clearly again?  

[DKHummer]

Maybe you have AADD. We live in a fast pass world today and I figure , in my case, That my Brain has 50 thoughts going on and it makes it Difficult to narrow down to that one Thought. Plus old age and CRS go together.  Can't Remember Shhhtuff.!  I'm also 45 with lots of Education , Today  I have lost interest on things I need to study , burnt out on learning, maybe it is Middle age ,  Heck, I don't Know!  Just Don't worry about it. I look at the elderly person saying Have a nice Day , as you leave Walmart, and I think what do i Have to be depressed about  I hope this made sense.
SMILE!! And Have a great Year!  David