Psychosis is a term used to describe mental disturbances that cause loss of contact with reality and disintegration of personality. Delusions -- false beliefs that don't match your knowledge of reality -- and hallucinations are the hallmarks of psychosis. Schizophrenia is the most familiar example of a psychotic disorder. Treatment of psychosis usually involves the use of medications that block the actions of neurotransmitters, specifically dopamine and serotonin, which are synthesized in your brain from the amino acids L-tyrosine and L-tryptophan.
Receptors
The biochemical abnormalities that lead to psychosis are far from straightforward. A December 2000 review in "The Journal of Pharmacology and Experimental Therapeutics" revealed that at least one type of dopamine receptor and two types of serotonin receptors are intimately involved in the generation of psychotic symptoms in schizophrenic patients. Blocking these receptors -- thus depriving them of dopamine and serotonin -- reduces psychosis in most, but not all, schizophrenic patients. However, such interference with neurotransmitter function causes serious and sometimes irreversible side effects, such as movement disorders.
Dopamine
The December 2001 issue of "Biological Psychiatry" suggests that dopamine is the central participant in psychosis, because medications that do not at least partially block dopamine receptors are ineffective for treating psychotic disorders. L-tyrosine, an amino acid that your body needs to synthesize thyroid hormones, is converted in your brain to dopamine, epinephrine and norepinephrine. These neurotransmitters play important roles in a variety of neurologic processes, including movement, mood, alertness, learning, memory, sleep, perception and motivation. They also participate in an array of physiologic activities, such as heart rate and blood pressure control.
Serotonin
Serotonin is produced by enzymatic conversion of the amino acid L-tryptophan in your brain and gastrointestinal tract. Its role in psychosis has been demonstrated in schizophrenic patients undergoing brain scans during psychotic episodes. A study published in the June 2002 issue of "Archives of General Psychiatry" demonstrated that schizophrenic patients possess a higher density of serotonin receptors in certain areas of their brains. Stimulation of these receptors, which causes "downstream" stimulation of dopamine receptors, presumably leads to the aberrant neurologic activity that causes psychosis. Like dopamine, serotonin is involved in many neurologic and physiologic processes in your body.
Considerations
Psychosis is driven by stimulation of receptors that respond to dopamine and serotonin, which are derived from L-tyrosine and L-tryptophan, respectively. The complex interactions among various types of serotonin and dopamine receptors -- and the presence of these receptors in tissues elsewhere in your body -- make it difficult to develop medications that effectively treat psychosis without causing unacceptable side effects. It may be the density of receptors in your brain, rather than neurotransmitter levels per se, which determines your risk for psychosis. Therefore, it is unclear if altering your intake of amino acids has any effect on psychotic symptoms.
References
- "The Journal of Pharmacology and Experimental Therapeutics"; Improving the Treatment of Schizophrenia: Focus on Serotonin (5-HT)1A Receptors; M.J. Millan; December 2000
- "Biological Psychiatry"; Dopamine D2 Receptors and Their Role in Atypical Antipsychotic Action: Still Necessary and May Even Be Sufficient; S. Kapur, G. Remington; December 2001
- "Archives of General Psychiatry"; Brain Serotoin 5-HT1A Receptor Binding in Schizophrenia Measured by Positron Emission Tomography and [11C]WAY-100635; J. Tauscher, et al.; June 2002
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