Fragile-X carrier females: evidence for a distinct psychopathological phenotype?

The present study examined 35 mothers (29 premutation carriers) of children with fragile-X syndrome in measures of intelligence and psychiatric disorders by comparing them with two control groups: a) 30 mothers of children in the general population and b) 17 mothers of non-fra-X retarded children with autism. Premutation carriers had a higher frequency of affective disorders than mothers from the general population. Preliminary data indicate that normally intelligent premutation carriers of the fra-X genetic abnormality have a similar frequency of affective disorders (DSM-III-R criteria [APA, 1987]) than mothers of autistic children. Neither carriers of the premutation nor carriers of the full mutation in the fra-X group obtained a diagnosis of the schizophrenia-spectrum (schizophrenia, schizophreniform disorder, and schizoaffective disorder). Carriers of the fra-X full mutation had considerably lower IQ than carriers of the fra-X premutation. There was a negative correlation between length of CGG repeats and IQ which failed to reach significance in both groups of fra-X carriers. Psychiatric morbidity was not restricted to carriers of the fra-X full mutation only but was also present in normal intelligent premutation carriers. Furthermore the age of onset of psychiatric morbidity in both groups of mothers of fra-X children as well as the group of mothers with autistic children was much earlier than the age when mental retardation had been diagnosed in their children. Increased psychosocial burden of raising a developmentally retarded child and/or feelings of guilt of being a fra-X carrier can therefore not fully explain our findings (three-fold higher frequencies of affective disorders compared to mothers from the general population).