Dopamine function and sensitivity is often heightened in people who experience psychosis, particularly those with schizophrenia. Elevated dopamine sensitivity has long been seen as a risk factor for a psychotic episode. But little research has examined if dopamine sensitivity is elevated in individuals who have a first degree relative with schizophrenia, although they themselves exhibit no signs of the illness. Because family members of a schizophrenic individual have an 80% chance of developing schizophrenia, this trait could be an important indicator to identify those at highest risk for psychotic symptoms prior to full onset of the illness. To address this issue, P. Shotbolt of the MRC Clinical Sciences Centre at the Hammersmith Hospital of the Imperial College in London conducted a study to see if close relatives of schizophrenic clients exhibited the same levels of dopamine function sensitivity as their family members who were receiving medication for the illness.
Shotbolt examined the 18F DOPA uptake in healthy fraternal and identical twin members whose co-twins had schizophrenia and were currently stable. He compared the dopamine functioning levels of the co-twins to those of 10 healthy fraternal twin pairs and found that the co-twins of the schizophrenic participants had normal levels of 18F DOPA, thus indicating no elevations in their dopamine function sensitivity. There was no difference in these findings regardless of whether the twins were identical or fraternal. Additionally, the schizophrenic twins, all of whom were stable and receiving medication, also showed no abnormal increases in dopamine sensitivity. Therefore, Shotbolt believes that these results reveal an important finding related to dopamine sensitivity in individuals at risk for or diagnosed with schizophrenia. Shotbolt said, “One possible interpretation of these findings is that elevated dopamine synthesis capacity is linked to the development of psychotic symptoms rather than a vulnerability to psychosis per se.” To further support this hypothesis, the well twins were evaluated an average of 15 years after their twin siblings had developed schizophrenia, thus decreasing the likelihood of symptom development. In conclusion, Shotbolt thinks that these results will be clinically significant in further exploring psychosis in clients with schizophrenia.
Shotbolt, P., Stokes, P. R., Owens, S. F., Toulopoulou, T., Picchioni, M. M., Bose, S. K., Murray, R. M., Howes, O. D. Striatal Dopamine Synthesis Capacity in Twins Discordant for Schizophrenia. Psychological Medicine 41.1 (2011): 2331-338. Print.
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