Neuropsychological Functioning in Adolescent Children of Mothers with a History of Bipolar or Major Depressive Disorders
Klimes-Dougan B, Ronsaville D, Wiggs EA, Martinez PE;
Commented by , 27 Sep 2006
Background
During recent years it has become increasingly evident that a proportion of patients with bipolar disorders or depressive disorder present with cognitive impairment, even following remission of affective symptoms. Depression seems to be a risk factor for developing of dementia and patients with depressive or bipolar disorders have been found to have increased risk of developing dementia.
It has been suggested that cognitive dysfunction is a trait factor that may be prevalent prior to the onset of affective disorders. However, only very few studies have investigated whether that is the case.
Method
As part of an ongoing longitudinal study of depressed mothers and their offspring conducted at the National Institute of Mental Health, U.S., adolescents offspring of mothers with bipolar depression (n = 43), major depressive disorder (n = 72) and of psychiatrically well parents (n = 50) were identified. Diagnoses of the parents were made using the Schedule for Affective disorders and Schizophrenia (SADS) and the Structured Clinical Interview for DSM-III-R (SCID).
Children with head injuries, developmental disabilities, epilepsy, or an IQ of less than 86 had been excluded. Mean age of the children was 15.6 + 2.6 years. Neuropsychological function was assessed using a large numbers of standardized tests.
Results
At the start of the study, mothers in the three groups had similar levels of education, but 12 years later mothers with depressive disorder or bipolar disorder had considerably lower education levels than control mothers and with asignificantly higher divorce rate. Children of mothers with bipolar depression showed deficits in executive function and selective deficits in spatial memory and attention, in comparison with children of well mothers.
These differences remained even after statistical adjustments for IQ, depressive or hypomanic symptoms of the children and adjustment of environmental characteristics such as maternal functioning as rated by the Global Assessment of Functioning (GAF) and family stress.
Deficits were not found for children of mothers with depressive disorder.
Professor Kessing's comments
This seems as a well-conducted study with intriguing new data. It remains to be investigated whether those children who presented cognitive deficits have greater risk of later developing affective disorders than those without. It is, however, mentioned in the paper that subsequent results showed that 78% of those young adults who later met criteria for bipolar disorder had shown impairment in tasks of executive functioning and attention before the formal diagnosis was made.
It is not possible from the study to discriminate the effect of genetic from the effect of environmental factors such as a dysfunctional family life on the risk of cognitive deficits in the adolescents. However, results from a newly published twin study suggest that cognitive impairment may be genetically transmitted (ref. 1).
Monozygotic High-Risk twins showed significant impairment on selective and sustained attention, executive function, language processing and working and declarative memory, whereas Dizygotic High-Risk twins presented with significantly lower scores only on language processing and episodic memory.
References
1. Christensen MV, Kyvik KO, Kessing LV. Cognitive function in unaffected twins discordant for affective disorder. Psychological Medicine 2006; 36 (8); 1119-1129. [Epub 2006 May 31]