Is it Alzheimer's disease or depression?

Mental Health Expert Dr. Charles Raison Psychiatrist,
Emory University Medical School

Expert answer

Dear Nina,

The nature of your question makes me suspect that whoever you are thinking about is someone who is older, whose behavior has changed and become more erratic, who is very anxious and unhappy and who is beginning to forget things or be confused. And I'm picturing someone who wasn't always like this. Am I on target?

In the old days, psychiatrists would debate whether this scenario reflected dementia or "pseudo-dementia" from the depression. "Pseudo-dementia" reflects the fact that older folks who get really depressed can get so slowed down and so confused that they look like they have dementia. But then, when their depression is successfully treated, their thinking and behavior goes back to normal. Problem solved.

Or so we thought. Unfortunately, however, we now know that if you follow older people who develop a new depression for several years, many of them will go on to develop Alzheimer's disease or a vascular dementia that results from multiple little strokes in the brain.

In this way, depression can be thought of as a first manifestation of the brain beginning to break down. As the breakdown worsens, depression shades into dementia. Said differently, the onset of depression in old age is often the first manifestation of dementia, a reflection of the brain beginning to fail. Treating the depression improves things for a while, but eventually the tide of brain destruction is just too great, and things go irreparably downhill.

A lot of recent scientific data suggest that there may be at least two different kinds of depression. One kind -- probably the most common -- is really a young person's illness, with a peak age of onset in the 20s and 30s. It is twice as common in women as in men, tends to be chronic and -- if one looks closely enough -- is often associated with mood swings that some scientists think reflect ties to bipolar disorder or manic depression.

The other type of depression tends to come on later in life, is closer to 50-50 in its sex distribution and is typically associated with evidence of vascular (i.e. blood vessel) disease in the brain. A recent study shows that family members of people who develop depression early in life tend to have depression themselves. On the other hand, family members of people with the second kind of depression (i.e. that starts late in life) tend to have family members with vascular disease rather than depression per se.

It is of utmost importance that you get your "someone" to a physician as soon as you can for a full evaluation for a number of reasons.

First, sometimes a depression is "just a depression," in which case the sooner you treat it the better the person will do. Second, sometimes the changes in thinking and behavior are from a reversible medical cause and therefore can be fixed. You'd be amazed how too much or too little thyroid activity can completely derail older folks and how quickly they can pop back to normal when thyroid function is normalized.

Finally, even if a person has early dementia, the sooner they can get on appropriate medications, the likelier they are to benefit from them.