The monoamine hypothesis is hypothesis that the monoamine neurotransmitters--serotonin, norepinephrine, and dopamine--are responsible for mental illness. Supposedly, deficiencies of serotonin and norephinephrine are linked to increased depression and anxiety, whereas an excess of dopamine is linked to schizophrenia. The reality is that if you look at neurotransmitter levels in untreated people with and without mental illness you don't find a statistically difference in neurotransmitter levels between those with and without mental illness. There also aren't any correlations to be found between the severity of an illness and neurotransmitter levels--severely depressed people don't have any less serotonin than mildly depressed people.
This isn't to say that neurotransmitters play no role--they clearly do something because when people go off of drugs that target these neurotransmitters (SSRIs, SNRIs, atypical antipsychotics, etc.) they experience a subsequent change in these neurotransmitter levels and often experience a relapse. However, it is too simplistic to say that depression, for example, is caused by low serotonin because it's not. We don't know what it's caused by. Perhaps the distribution of neurotransmitters is what's important.
It seems to me that there's enough evidence to say that there is some sort of complicated link between neurotransmitters and mood. But the monoamine hypothesis is too simplistic in a number of ways:
We seem to have capitalized on the possibility that the monoamine hypothesis is true, because it would be convenient if it were. Not to mention profitable for the pharmaceutical industry. And most people, psychiatrists, and doctors, seem to think that the monoamine hypothesis is true. Just watch an ad on TV for an antidepressant, "Depression is caused by a chemical imbalance in the brain. Such-and-such drug can fix that imbalance." Not true!
Just to note, the monoamine hypothesis in and of itself doesn't mean that antidepressants don't work. They could work (or do something weird), but they don't fix a chemical imbalance in the brain because there is no measurable chemical imbalance in the brain. If they do work (or do something), they do it by causing an imbalance in the brain.
This isn't to say that neurotransmitters play no role--they clearly do something because when people go off of drugs that target these neurotransmitters (SSRIs, SNRIs, atypical antipsychotics, etc.) they experience a subsequent change in these neurotransmitter levels and often experience a relapse. However, it is too simplistic to say that depression, for example, is caused by low serotonin because it's not. We don't know what it's caused by. Perhaps the distribution of neurotransmitters is what's important.
It seems to me that there's enough evidence to say that there is some sort of complicated link between neurotransmitters and mood. But the monoamine hypothesis is too simplistic in a number of ways:
- It ignores what I think ought to be considered at least an equally important contributing factor to mental illness: structural differences in the brain. There's evidence that people with generalized anxiety and depression have more gray matter in certain parts of their brain and less in others, whereas people with OCD have the reverse proportions of gray and white matter. It's also been shown that you can induce OCD-like behaviors in animals by damaging their basal ganglia.
- The monoamine hypothesis also seems to ignore hormones. We know that mood changes can occur in conjunction with menstruation, pregnancy, and being a teenager, so it has to be a vast oversimplification to say mental illnesses are caused by total neurotransmitter levels alone. I haven't really seen anything on hormones directly affecting neurotransmitter levels, so I tend to think that they affect mood by a separate mechanism from neurotransmitters.
- Like I mentioned before, perhaps the distribution of neurotransmitters or what neurotransmitters do to the structure of the brain may be important. The monamine hypothesis only speaks of total levels. SSRIs might do something (it's unclear to me what they do) because they increase serotonin everywhere in the brain. Or flooding the brain with serotonin might induce structural changes. Who knows? This is conjecture.
We seem to have capitalized on the possibility that the monoamine hypothesis is true, because it would be convenient if it were. Not to mention profitable for the pharmaceutical industry. And most people, psychiatrists, and doctors, seem to think that the monoamine hypothesis is true. Just watch an ad on TV for an antidepressant, "Depression is caused by a chemical imbalance in the brain. Such-and-such drug can fix that imbalance." Not true!
Just to note, the monoamine hypothesis in and of itself doesn't mean that antidepressants don't work. They could work (or do something weird), but they don't fix a chemical imbalance in the brain because there is no measurable chemical imbalance in the brain. If they do work (or do something), they do it by causing an imbalance in the brain.
What are your associations with ssris? Do you personally know anyone who has been on them, found them useful or not useful? Do you have emotional associations with them one way or another?
ReplyDeleteOne of the difficult thing about them is that very few people are objective on them. People are usually pushing a point of view, so I have a hard time really knowing what to think. You have a bunch of reasons against them, probably good reasons, but I also get this impression that you may have negative associations that come before your reason as well.
I've known people who have seemed to get benefit, and I've also known people who have killed themselves on them. I used to be very uncomfortable with the idea of them but now, I'm not really sure what i think.