neurotransmitters in relation to depression; what might be an example of this at work?

[vincentfromyay]

i'm particularly interested in serotonin, but also in dopamine and norepinephrine

[PhDwannabe]

What exactly is your question?

[herbbread]

Did you have any particular question regarding serotonin and depression? In general, serotonin levels, and many of the precursors for the generation of the particular neurotransmitter, tend to be lower in people with depression. That's the reason behind the use of SSRIs (selective serotonin reuptake inhibitors) in people with depression. By blocking the reuptake of serotonin in the synaptic cleft, you increase the amount of time the neurotransmitter remains active at the synapse, and compensates for any deficiency in serotonin there might be. There's a ton of neuroscience/neurology research going about about this. Is there something specific you wanted to know?

 

There's a good article reviewing the pathology between serotonin and depression that might be useful:

[PhDwannabe]

Actually, there is a fair amount of accumulating evidence that the serotonin hypothesis is vastly oversimplified, and what we are seeing in what are admittedly fairly low-effect size results associating low serotonin levels and depression is really one branch of a far more complex process which has largely yet to be observed. This guy's blog post is relatively informative on the matter for the, well, between-layperson-and-scientist, and has a lot of good links if you'd like to see some of the empirical work. People tend to take it for granted that this bit of science is settled, and that certainty is often unreconciled with this fact that, well, drugs that agonize monoamines like serotonin don't even work that well. Their clinical effects are modest at best, and often barely make it above rates of improvement seen in placebo control conditions.

 

At any rate, neurotransmitter explanations get you relatively little in terms of the whole story anyway, since neurochemical interactions are a grand mediator of all behavior, cognition, emotion--essentially everything we do and experience. To refer to neurotransmitter deficits or excesses as causal--as the start of the story, as it were--is problematic for about a million reasons on its own.

[vincentfromyay]

@PhDwannabe; myquestion is, are there examples of a lack of a neurotransmitter, say,serotonin, causing a problem for someone with depression. Eg, could it bedemonstrated that a depressed person’s inability, or difficulty, in say,getting up out of bed, was due to the electrochemical signal not crossing therelavant synapses due to there not being enough serotonin, or due to theavailable serotonin not being available in the synapse for long enough?

 

Also in relation to ssri’s not shown to have much moreeffect than placebo; the wiki page on FLUOXETINE says otherwise

 

 

@herbread; you said, “...serotonin levels... tendto be lower in people with depression...” is there evidence for this?

 

[PhDwannabe]

Vincent, I don't know why you're typing in Courier, but it hurts the eyes.

 

No, it cannot be demonstrated that

a depressed person's inability, or difficulty, in say,getting up out of bed, was due to the electrochemical signal not crossing therelavant synapses due to there not being enough serotonin, or due to theavailable serotonin not being available in the synapse for long enough?

At least, not empirically. There are plausible and relevant causal agents here that are not amenable to direct experimentation. This is as much a philosophy of mind issue as it is a neurobiological one.

 

Also in relation to ssri's not shown to have much moreeffect than placebo; the wiki page on FLUOXETINE says otherwise

Wikipedia's the best place to start and the worst place to end. Drug treatment outcome studies have a worrisome habit of waving the flag of success when treatment differences reach statistical significance. Statistical significance is not clinical significance. Effect sizes, which are roundly ignored in popular reports of these studies, are frequently disappointing. Go read some of them and look at the effect size statistics in their results sections. If you're unfamiliar with this thing called "effect size," go back to your friend Wikipedia.

 

"...serotonin levels... tendto be lower in people with depression..." is there evidence for this?

Plenty of evidence for this. Why don't you look at the article he provided? While I continue to maintain that the story is extremely complex and really quite poorly explained by mere serotonin differences, that bare fact as stated is an empirically measurable, and empirically measured, one.

Edited October 1, 2011 by PhDwannabe