Genetic influences

Future Outlook for Pharmacologic Treatment of Abuse and Dependence. The importance of the psychosocial dimension ia predisposiag iadividuals toward substance use disorders and subsequentiy maintaining the disorder caimot be overestimated. Additionally, genetic influences have been found to exert an important influence on HabiUty for dmg abuse. A high comorbidity of psychiatric illnesses with substance use disorders further compHcates therapeutic iaterventions ia such patients (236). 

Schizophrenia is not a neurodegenerative disease but there is some general neuropathology. There is also evidence for a genetic influence. In monozygotic twins with... 

I The occurrence of MDD shows a familial pattern because first-degree relatives of MDD patients are about three times more likely to develop MDD compared with first-degree relatives of normal control individuals. Adoption studies and twin studies reveal that the familial aggregation of MDD is due to genetic influences.5... 

AML represents a group of disorders in which both failure to differentiate and overproliferation in the stem cell compartment produce an overabundance of nonfunctional cells termed myeloblasts. While the specific cause for this biologic abnormality is unknown, an understanding of the genetic influence of leukemia is leading to a wide variety of targeted therapies.9... 

Smith MW, Dean M, Carrington M, et al. Contrasting genetic influence of CCR2 and CCR5 variants on HIV-1 infection and disease progression. Science 1997 277 959-965. 

O Connor S, Sorbel J, Morzorati S, Li T-K, Christian JC. A twin study of genetic influences on the acute adaptation of the EEG to alcohol. Alcohol Clin Exp Res 1999 23 494-501. 

Likelihood of developing dependence to nicotine will involve specific functional changes in the brain. Examining the detailed genetic basis for these functional changes is difficult in humans, so animal models are needed. Three approaches have been taken to examining genetic influences of the effects of nicotine in rodents namely inbred lines, selectively bred lines and knockout mice. 

If all biotic and abiotic factors can be controlled, genetic influence is one of the major features responsible for differences in phytochemical composition. Several reviews on diverse compounds have reported the genetic influence on phytochemicals, sometimes to a surprising order of magnitude. The influence of cultivar can be even greater than the influence of growth conditions, thus complicating the data analyses for plant composition. 

I distinguish between theoretical and practical conclusions because theoretically we are interested in the degree of genetic influence on a latent trait or theoretical construct. Practically we may be interested in the heritability of a specific measure (e.g., IQ as measures by the Wechler Adult Intelligence Scale). An excellent discussion of measurement eror in psychological research can be found in Schmidt and Hunter (1996). 

Contrary to Staples claim, the evidence for genetic influence on IQ has become much stronger in recent years and a number of important discoveries have been made. I summarize the key findings in a few tables and figures. Table 5 shows the most direct evidence regarding the heritability of IQ, the correlations for monozygotic twins reared apart.2... 

Critics of the MZA data who argue that various forms of bias (placement, rearing by relatives rather than random placement, etc.) probably lead to serious overestimates of genetic influence seldom address both the MZA and URT data sets simultaneously (Dorfman, 1995 Fancher, 1995). Since URTs live in the same home and are matched on far more variables than MZA twins, the whole array of commonly cited biases in MZA studies is brought into question. I used to call this kind of selective reporting pseudo-analysis (Bouchard, 1982) until I discovered it already had a name. It is called the Neglected Aspect Fallacy (Castell, 1935) and it violates Carnap s Total Evidence Rule (1950). 

Plomin, R., Lichtenstein, P., Pedersen, N. L., McCleam, G. E., Nesselroade, J. R. (1990). Genetic influences on life events during the last half of the life span. Psychology and Aging, 5, 25-30. 

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