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Chemical imbalance theory from Wikipedia

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Chemical imbalance theory from Wikipedia

Postby Guest » Sat Nov 12, 2005 10:08 pm


Chemical imbalance theory

Chemical imbalance is a term used by drug companies in the United States in advertising and consumer literature for psychoactive drugs after deregulation of pharmaceutical advertising. The term refers to a series of hypothesised neurochemical changes once thought to underly mental illness.

Chemical imbalance theory is not a scientific theory, but refers to the lay conception of a theory generated by the use of the term 'chemical imbalance'. Current research in neuroscience does implicate roles for changes in the operation of neurotransmitters in the brain, and changes in neurons and neural structure, but current models are more complex than simple chemical balances/imbalances.

Chemical imbalances

Changes in levels of neurotransmitters and other neural level phenomena are hypothesised to be the underlying psychopathology for certain mental illnesses, notably clinical depression and schizophrenia. In 1965, Joseph Schildkraut hypothesized that depression was associated with low levels of norepinephrine in the brain, and later researchers thought serotonin might be the culprit.[1]] Initially, relatively simple changes in the level of these neurotransmitters were thought to be found in individuals with depression. However, advanced findings began to fine tune the more simple explanations. For example, certain drugs used to treat depression were found to change the levels of neurotransmitters for several days, but then return to normal, well before any effect was observed on the depressive episode. Such findings implicate more complex mechanisms, such as changes in neurotransmitter production, transmission, re-uptake, and neural sensitivity.

In addition to depression, changes in levels of neurotransmitters have also been implicates in anxiety disorders, bipolar disorder (manic depressive disorder), schizophrenia, and Parkinson's disease. As well as changes in serotonin and norepinephrine, dopamine systems have also been considered.

So, rather than being caused by simple chemical imbalances, mental illness is widely recognized to be caused by complex chemical imbalances.


Critics of the chemical imbalance contend brain chemistry levels are not an adequate gauge of neurochemical processes affecting mental health, noting the enormous number of different chemicals and their unknown interactions. Moreover, critics assert, the psychiatric establishment assumes patients having a ‘mental illness’ must have a ‘chemical imbalance’ in their brain, as subjective diagnostic checklists are used in lieu of actual medical tests. These criticisms appear at odds with current research, however, but may be relevant to professionals who were trained less recently.

Even if neurological and neurochemical differences are associated with certain behaviors, the practice of pathologizing these behaviours has been questioned. Because neural mechanisms imply a physiological pathology underlying mental illnesses, they appear to justify the use of medication in treatment. Critics argue that the legitimacy given to medication by neural mechanisms can lead to an over-reliance on medication. Similarly, the perceived efficacy of medication as a treatment implies an underlying neural mechanism. A further issue is the extent to which research into neural mechanisms and the efficacy of medication is funding by pharmaceutical companies, who have an obvious vested interest in the use of medication.

The chemical imbalance theory, according to critics, is routinely presented as ‘fact’ so often it has become widely accepted as fact, despite having been challenged repeatedly. The Pfizer drug company has been promoting Zoloft for years with saturation marketing, in print, on television, and on the radio, starring a miserably depressed ovoid creature. The ads assert mental illness may be due to a chemical imbalance in the brain, and that "Zoloft works to correct this imbalance." Without mentioning its own name, Eli Lilly urges viewers to seek treatment for depression, and to visit their website, DepressionHurts.com, because "Many researchers believe depression is caused by an imbalance of naturally occurring chemicals, serotonin and norepinephrine, in the brain and the body."

According to Jaelline Jaffe and Jeanne Segal, "The misconception the commercials foster is that the brain somehow develops a chemical imbalance and the result is depression, occurring in a single directional process. In fact, the relationship between brain chemistry and experience is a two-directional phenomenon: Life experience affects brain chemistry at least as much as brain chemistry affects life experience. The 'chemical imbalance' hypothesis is not wrong. It's just not entirely correct.'

Psychiatric diagnostic practices in the United States have come under sharp criticism for reliance upon the chemical imbalance theory rather than actual medical testing. For example, in a 1980's Florida psychiatric hospital study, one hundred patients diagnosed with a mental illness were subsequently given a complete medical exam, after which it was discovered nearly half of the patients’ psychiatric problems were secondary manifestations of an undiagnosed medical problem.[2] Despite that finding, the author of the study, psychiatrist Mark Gold, is a strong advocate that addiction and psychiatric disorders are rooted in complex chemical imbalances and effective treatment is available from various drug treatments.

Diagnostic utility

There are advanced imaging techniques such as Positron Emission Tomography (PET Scans) that can test for chemical imbalances. Changes in levels of neurotransmitter metabolites are detectable in urine and cerebrospinal fluid and have been associated with certain mental illnesses, but are not sufficiently predictive for successful diagnosis.

Thus, Psychiatric diagnoses are usually made based on algorithmic (DSM-IV) criteria outlined in diagnostic manuals, primarily through reference to the Diagnostic and Statistical Manual of Mental Disorders (DSM). In practice, psychiatric diagnoses rely upon a physician's judgments about a patient's medical history, clinical evaluation of symptoms, and from patient response to psychiatric drugs.

Pharmaceutical company literature continues to explain the operation of psychoactive drugs in terms of chemical imbalances, and restoring a chemical balance closer to 'normal'. The research underlying the mechanism by which the drugs are thought to work is typically justified by clinical trials demonstrating their efficacy.

Cautionary measures

An important consideration with regard to chemical intervention is the potential for relapsing into depression or other psychiatric conditions when medication is discontinued abruptly or without medical supervision. Aside from malnutrition, the only certain means of creating chemical imbalances in the brain is the use of psychiatric drugs, and side effects from psychiatric drugs can be significant. Great care must be taken to prevent severe withdrawal symptoms after engaging in psychiatric drug use.

Pyschiatric drugs influence levels of neurotransmitters in the brain, and perhaps underlie the genesis of the term 'chemical imbalance theory'. However, rather than restoring 'normal' levels of neurotransmitters in the brain, they frequently attempt to compensate for changes in sensitivity to or production of neurotransmitters, usually in a relatively isolated part of the brain (despite the drug changing more global levels of the neurotransmitters). Most disorders treated with medication have a hypothesised neural mechanism.

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