Chemical imbalance hypothesis of mental disorder

Chemical imbalance is a term sometimes used by drug companies in the United States in advertising and consumer literature for psychoactive drugs after the deregulation of pharmaceutical advertising. The term has its origins in the 'chemical hypothesis', which refers to a series of hypothesised neurochemical changes once thought to partially underly mental illness. The chemical hypothesis does not reflect current scientific knowledge, and the term chemical imbalance is most often used by groups critical of the pharmaceutical treatment of mental illness. Because the chemical hypothesis is no longer accepted, the use of chemical imbalance by pharmaceutical companies might be considered a lay explanation.

Chemical imbalance theory was never a scientific theory. Current research in neuroscience does indicate roles for changes in the operation of neurotransmitters in the brain, and changes in neurons and neural structure in the pathophysiology of mental illness, but current models are more complex than simple chemical balances/imbalances. Causality (i.e. whether neurotransmitter changes cause mental illness or whether mental illness affects neurotransmitter levels) is uncertain.

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.] 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 implicated 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, while all biology is essentially chemical in nature, rather than being caused by simple chemical imbalances, mental illness is now widely recognized to be caused by complex and, in many cases, as-yet unknown factors. According to Jaelline Jaffe and Jeanne Segal:
 * "The misconception the [drug] 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."

Use of drugs to correct
Psychiatric drugs influence levels of neurotransmitters in the brain, and perhaps underlie the genesis of the term 'chemical imbalance theory'.

Most people believe that the psychiatric drugs, such as antidepressants, 'correct,' or move towards average levels, the levels of neurotransmitters in the brain. However, rather than restoring 'normal' levels, these drugs frequently attempt to compensate for changes in sensitivity to or production of neurotransmitters, with newer drugs acting in a relatively isolated part of the brain (although some drugs act on a larger scale).

Limitations on the use of medications
Most disorders treated with medication have a hypothesised neural mechanism, but it is important to note that chemical imbalances are not believed to explain all psychiatric differences, nor are medications used to treat all neurological or psychiatric issues. Some mental illness, such as some patients with 'pure' Borderline Personality Disorder, may not have a significant biochemical basis underlying it; these patients will typically not find that their symptoms are usefully treated with drugs. Similarly, when significant neuroanatomical differences are involved, the effectiveness of drugs is limited. For example, autism researchers have found differences in gray and white matter volumes, neuron size, brain mass, and locus of brain function; differences which may be accounted by unknown factors, perhaps involving the interaction of 15 to 100 different genes.

Controversy
Critics contend that psychiatric drugs, intended to alter neurochemical processes by manipulating neurotransmitter levels, are not always efficacious, not always safe, and not necessarily a scientifically sound method for improving mental health. The number of different chemicals in the brain and their unknown interactions limit understanding and increase the likelihood of unforeseen complications. Moreover, critics assert, the psychiatric establishment merely assumes patients who are diagnosed with a given mental illness always have a chemical imbalance in their brains, even though behavioral checklists, and not actual chemical measurements, are used to reach a diagnosis.

Psychiatric diagnostic practices in the United States have come under criticism for over-reliance upon these behavioral checklists rather than thorough, whole-body medical testing. For example, in a Florida psychiatric hospital study from the 1980s, 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, such as hypothyroidism mimicking depression. Most, if not all, hospitals in the United States currently require a medical exam be done on all patients admitted to an inpatient psychiatric unit. The author of the study, psychiatrist Mark Gold, remains a strong advocate that addiction and psychiatric disorders are rooted in complex chemical imbalances and that effective treatment is available for most correctly diagnosed psychiatric patients from various drug treatments -- an opinion that he shares with the majority of the medical community.

Even when neurological and neurochemical differences are associated with certain behaviors, the practice of pathologizing these behaviours has been questioned by some activists and people who have been diagnosed with mental illnesses. Because neural mechanisms imply a physiological difference 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.

Critics also allege that pharmaceutical companies have a conflict of interest when they fund research into biochemical mechanisms behind mental illness and the efficacy of medication at reducing behavior differences.

Further controversy is engendered by the links between certain critics of psychiatry and the Church of Scientology. While Anti-psychiatry is not equivalent to Scientology, Scientology maintains several organizations like the Citizens Commission on Human Rights which have been outspoken critics of the biological basis of mental illness, sponsoring websites critical of "chemical imbalance". Here also, there may exist a substantial conflict of interest as Scientology advocates and sells an alternative and expensive non-pharmacological treatment known as Dianetics.

Popular culture and advertising
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. For example, Pfizer has heavily promoted its antidepressant drug, Zoloft, with ads asserting that 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."

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 psychotropic chemicals, a category which includes both legal prescription drugs and illegal drugs like LSD or cocaine. Side effects from psychotropic drugs can be significant. Great care must be taken to prevent severe withdrawal symptoms after using psychotropic drugs. Neuroleptic drugs (typically used in the treatment of schizophrenia) are particularly dangerous to withdraw from quickly. Rebound psychosis is common and can leave a patient more unstable than they were prior to taking the neuroleptic in the first place.

Current neuroscience perspectives

 * Evidence-based medicine
 * Neurochemistry
 * Neuroscience
 * Neurotransmitter

Critical perspectives

 * Anti-psychiatry
 * ICSPP
 * Mindfreedom.org

Current neuroscience theories

 * Neurobiology of depression. Neuron. 2002 Mar 28;34(1):13-25.
 * Is mood chemistry? Nat Rev Neurosci. 2005 Mar;6(3):241-6. Implicates change in information processing not 'chemical imbalance'.

Critical views

 * CCHR - Scientology-affiliated Psychiatric Watchdog Speaks Out About Tom Cruise Speaking Out on Antidepressants
 * 23NLPeople.com - 'Ritalin: Role Models in a Bottle, Social Discipline in a Capsule'
 * ETFRC.com - 'There are no "Chemical Imbalances"', Eaton T. Fores Research Center Against Psychiatry
 * PsychForums.com - Online discussion of ETFRC's 'There are no "Chemical Imbalances"'


 * HappinessOnline.org - 'I'm O.K. You're O.K. We're Not O.K. Some psychiatrists want to start treating "relational disorders." Are they nuts?', Walter Kirn, Time (September 16, 2002)
 * Keirsey.com - 'The Great A.D.D. Hoax', David Keirsey
 * MindFreedom.org - 'Debate Between Pfizer, Inc. and MindFreedom continues: Three Rounds, So Far: MindFreedom Calls for Congressional Investigation of Psychiatric Drug Company Undue Influence and Corruption in Federal Agencies'
 * Oikos.org - 'History of the Fraud of Biological Psychiatry', F. Baughman
 * PLoSJournals.org - 'Serotonin and Depression: A Disconnect between the Advertisements and the Scientific Literature', Jeffrey R. Lacasse, Jonathan Leo, Public Library of Science Medicine, vol 2, no 12 (November 8, 2005)
 * StopShrinks.org - 'Logical Errors in Mental Health', Rob Ryley
 * ThomHartmann.com - 'The Gift of ADHD: ADHD and ADD Home Page', Thom Hartmann
 * ZMag.org - 'Psychiatric Medications, Illicit Drugs, & Alcohol', Bruce Levine (2002)

Proponent views

 * Anxiety-and-Depression-Solutions.com - 'Understanding Chemical Imbalance: What is a Chemical Imbalance?', Jake Van Der Borne (14 June 2004)
 * BMA-Wellness.com - 'Frequently Asked Questions About Psychiatry and Mental Health', Floyd P. Garrett, MD
 * HelpGuide.org - 'Medications for Treating Depression and Anxiety: Making Informed Choices', Jaelline Jaffe, PhD, Jeanne Segal, PhD
 * MHSource.com 'Ask the Expert: Chemical Imbalance' (February 2001)
 * Zoloft (Sertraline HCl)