Is depression always triggered or can it just happen?

[Into The Light]

i was reading about bi-polar and that it's sudden mood swings to mania or depression for absolutely no reason at all. a person can be having a good time and 20 minutes later be really depressed.

i was wondering for those with unipolar depression what causes it. i know there are environmental and biological factors (vulnerability), but does it take some kind of event or series of events for a person to become clinically depressed? it makes sense to me that a major loss or a traumatic experience plunges a person into depression, but can it creep up on you out of the blue for no reason at all?

 

[forgetmenot]

I think yes one can be so busy in their life they are not realizing their own needs and slowly without notice they find themselves depressed and are unable to deal with the emotion.

 

[Daniel E.]

but can it creep up on you out of the blue for no reason at all?

I definitely think so, e.g.

Depression, once it sets in, is often a difficult neurological disorder to reverse, Poulter said.

http://forum.psychlinks.ca/depressi...-dna-changes-in-major-depression-suicide.html

OTOH, as with bipolar disorder, stress can be a significant trigger, as mentioned in the same article:

The effect of the chemical was to lower the activity of a gene known to be involved in coping with stress.

In animal studies to model depression treatments, they sometimes stress out rats until they act "depressed," e.g. can't swim as much.

And, as you know, there are always things that can be done to lessen not only the frequency of relapses but also their intensity and duration, including the obvious:

Monthly Therapy Prevents Depression Relapse | Psych Central News