Short answer:
It seems like you’re probably asking about the validity of the “chemical imbalance” idea as an explanation for your thoughts and feelings. I ended up writing quite a lot about this because it interests me but I realize you don’t necessarily want to slog through all of my admittedly dense prose. In brief, I think that:
1) The “chemical imbalance” idea is related to sound scientific observations, but it is not a complete theory of the processes behind mental illness. As far as I know, there are not highly specific “optimal” levels of neurotransmitters that have been identified, and it may be that good mental health is possible throughout a wide range of levels of neurotransmitters.
There is evidence that drugs that alter neurotransmitter levels help many people with mental illness achieve states of mind that are considered “better”, but in my opinion it is not the case that changing neurotransmitter levels alone is equivalent to “fixing mental illness”. It can be a helpful step in that direction, and in some people might even be necessary, but it is rarely sufficient. The rest of the “fixing” comes through one’s efforts to change how they respond to things so that their actions are helpful and less harmful than they were in the past.
2) Drugs are worth trying, but it’s very rare that they seem to eliminate your problems like a magic bullet. It’s more like they help you help yourself. Also, it’s best to do some sort of talk therapy in addition to drugs.
Long answer:
I’ve tried to provide the best summary I can because this seems like a relatively common question and I think it’s rarely very well explained to laypeople by the brief statements in drug FAQs, commercials for medications, and so forth. Obviously I am NOT by any means an expert in the field but I’ve read a decent bit about it and I believe all of the following info is correct and verifiable. There are some statements that are simply my opinions and I have tried to mark them as such.
The term "chemical imbalance" is used to refer to theories that propose the biological basis of mental disorders is related to the levels of various neurotransmitter substances in the brain.
I say “basis” rather than “cause” to emphasize that although the actions of neurotransmitter chemicals and neurons are always the proximate causes of thought, they are themselves affected by many different factors including genetics, past and current environmental stimuli, physical damage to the nervous tissues, psychotropic drugs, etc. (cf.
http://www.mayoclinic.com/health/dep...SECTION=causes )
The “chemical imbalance” idea extrapolates from what we know about how the brain works. The next paragraphs are a (hopefully accurate) overview of how brain cells communicate, and the fifth addresses how drugs can affect that process.
Neural Processes
Basically, your brain consists of about a hundred billion neurons that are intricately interconnected to each other (and plenty of other associated cells that help neurons work, but I won’t focus on that stuff here). There are several hundred trillion synapses (interconnections) between all those neurons in an adult human, so it’s a very complex network.
Neurons interact with each other electrochemically and the upshot of all that interaction is what you experience as sensory perception and what you think and what actions you take. Though of course we don’t fully understand how the brain gives rise to the mind, and there are a range of scientific and philosophical views on that subject.
Anyway, neurons use the energy they get from oxidizing food molecules (glucose, etc.) to concentrate lots of like-charged ions on the same side of a given semi-permeable membrane, such as doesn’t otherwise happen because like charges repel each other. Then, the neuron can open a “gate” in the membrane in response to sufficient electrical stimulation (as in the case of “voltage-gated ion channels”), or in response to the binding of a chemical messenger molecule (“ligand-gated ion channels”).
Opening the gate allows an electrical current to flow, as the ions that have been stored behind a membrane repel each other. So an electrical signal is conducted along the neuron, and this signal can in turn stimulate other neurons, either by directly inducing a change in potential difference (voltage), or by causing signaling molecules (neurotransmitters) to be released from the signaling neuron, which cross the synaptic gap and bind to receptors on the signaled neuron.
Psychotropic Drugs
It’s the action of neurotransmitters that virtually all psychotropic drugs affect. The goal is to change how frequently brain cells are stimulated by the action of substances binding at the neurotransmitter receptors, and accordingly how often the cells release electrical pulses which signal other neurons. Different drugs do this through different mechanisms, and many affect some neurotransmitters (much) more than others. Some change the rate at which the body naturally breaks down neurotransmitters (e.g. MAOIs); some interfere with the binding of neurotransmitters at their associated receptor sites on neurons (e.g. most antipsychotics are dopamine blockers); some cause the neurotransmitters to be reabsorbed by the signaling neuron less frequently, so that they stimulate the signaled neuron more often (e.g. SSRIs, SNRIs); some stimulate the neural receptors themselves (so that they’re activated more frequently than they would be by endogenous neurotransmitters alone), or are metabolized into substances that do so (e.g. dopamine agonists that are commonly used to treat Parkinson’s disease among other things).
Neurotransmitter Levels vis a vis Mental Illness
The “imbalance” being referred to in the theory, is the observation that on average, patients with various mental disorders have different levels of one or more neurotransmitters in their brains than control populations (i.e. those not diagnosed with mental disorders).
However, the levels of neurotransmitters in the brain also vary to some degree among people who are not mentally ill, and vary over time in a person in response to stimuli, circadian rhythm, and so forth. As far as I know, there are not currently any highly specific and universally agreed upon levels of the various neurotransmitters that are considered optimal for mental health.
I would suspect that there is not simply one highly specific set of levels of these chemicals that is “best” for everyone. Obviously personalities vary quite a bit in the population as a whole, and this reflects differences in brain structure and function. [Although, overall brain function involves things other than simply neurotransmitter levels, such as the structure of one’s neural network and patterns of electrochemical activation within that network, both of which are potentially affected by neurotransmitter levels.]
There is not just a single type of personality that is universally regarded as “best”, and in terms of natural selection it seems like a good idea to have a variety of cognitive approaches to problems within the population. [In fact, I think that’s why mental disorders are relatively common in the first place despite being apparently maladaptive: they are simply exaggerated (through random mutation, recombination, etc.) degrees of traits that in more moderate forms are adaptive. cf.
http://www.nytimes.com/2010/02/28/ma...ression-t.html ]
There’s still a lot more research to be done in this area, and for the time being neuropsychiatry is not a highly exact science. But from a pragmatic clinical perspective, what’s more important than one’s neurotransmitter levels (which are rarely measured in the course of psychiatric therapy anyway) is that they are subjectively feeling better and objectively more able to respond to stressors in adaptive (helpful/successful) ways.
The Utility of Drugs as a Treatment Method
The above mechanics of the nervous system aren’t really disputed, and there is statistical evidence that changing the levels/action of neurotransmitters produces changes that are regarded as positive in many patients with psychological problems.
However, there is a lot of debate about the extent to which simply altering the action of neurotransmitters in the brain is the best possible treatment for mental disorders. It is a relatively “crude” method of affecting how the brain processes information, which is a very complex process that’s still not fully understood. And the effective treatment of mental disorders depends on changing how the brain processes information, not simply on how many milligrams per liter of a given neurotransmitter is present in one’s brain at any given time. This makes mental disorders a lot harder to treat than simpler somatic illnesses like diabetes, where ensuring that the level of insulin in one’s bloodstream is within a certain range (and that one’s diet follows certain rules) will in fact reliably manage the problem. When it comes to mental disorders, changing neurotransmitter levels is not always (and probably not even usually, given the treatment statistics I’ve seen for various conditions) enough to “fix the problem” on its own.
Side Effects
Also, all psychotropic drugs can cause undesirable side-effects, which can vary in severity from being barely noticeable (fortunately this is currently the case for me at eight months on escitalopram; cf.
http://www.drugs.com/sfx/escitalopram-side-effects.html) to being arguably worse that the disease in some cases.
For example Lithium has long been known as an effective mood stabilizer but can substantially interfere with normal nervous system and heart function to a degree that can be dangerous and cause permanent damage with acute overdose or long-term use, and there is not a very large margin between the therapeutic dose usually required and the dose that can be dangerous and damaging; cf.
http://www.drugs.com/sfx/lithium-side-effects.html .
Please note that I’m not trying to promote or disparage either of the above example drugs or to compare them directly to one another; they’re not really indicated for treatment of the same conditions for the most part. They were just some of the best examples of side effect profiles that I could think of.
Drug research has given modern psychiatrists many more tools than they used to have, and accordingly I think it’s substantially rarer today for people to be prescribed things that are subjectively worse than their original disease, especially involuntarily. However, that does still happen sometimes, primarily in cases where people are persistently violent or suicidal and don’t respond to other treatments.
Further Reading
The following Wikipedia articles give a decent overview of the relevant subjects. Of course you should be skeptical of statements in Wikipedia that aren't cited or that are cited only by a source that doesn't seem very reputable/authoritative. But in general I think these articles are decently objective and well-cited.
Obviously I’ve chosen to err on the side of giving too much information, covering a lot of the concepts I talked about above even though some are substantially less central to the topic than others. I’ve tried to order them so those higher up the list are more relevant and crucial:
http://en.wikipedia.org/wiki/Chemical_imbalance
http://en.wikipedia.org/wiki/Causes_of_mental_disorders
http://en.wikipedia.org/wiki/Mental_disorder
http://en.wikipedia.org/wiki/Neuron
http://en.wikipedia.org/wiki/Synapse
http://en.wikipedia.org/wiki/Chemical_synapse
http://en.wikipedia.org/wiki/Neurotransmitter
http://en.wikipedia.org/wiki/Monoamine_neurotransmitter
http://en.wikipedia.org/wiki/Psychiatric_medications
http://en.wikipedia.org/wiki/Ssri#Mode_of_action
http://en.wikipedia.org/wiki/Maoi#Mode_of_action
http://en.wikipedia.org/wiki/Antipsychotics#Drug_action
http://en.wikipedia.org/wiki/Neuroscience
http://en.wikipedia.org/wiki/Coulomb_force
http://en.wikipedia.org/wiki/Voltage_gated_ion_channel
http://en.wikipedia.org/wiki/Ligand-gated_ion_channel
http://en.wikipedia.org/wiki/Cellular_respiration
http://en.wikipedia.org/wiki/Redox
