The majority of bipolar offspring will not develop bipolar disorder. It is therefore crucial to detect, from an early age, predictors of bipolar development in this high-risk population . Early detection of a prodromal state may allow timely and specific interventions and prevention of a poorer outcome.
Research on prodromal signs in this population did not give definite results. Carlson and Weintraub  found that attentional and behavioural problems during childhood were not more frequent in the offspring of bipolar parents than in the offspring at risk for other, non-bipolar, psychiatric disorders. However, a unique relationship between childhood problems and young adulthood mood disorders was found only in the bipolar risk group. Fergus et al. , based on parental retrospective report, suggested that the earlier of these childhood problems clustered around irritability/dyscontrol, i.e. temper tantrums, poor frustration tolerance, impulsivity and agressivity.
Preschool children with depression and a family history of bipolar disorder show higher rates of restlessness or motor agitation, compared to depressed children without family history of bipolar disorder . Follow-up studies are needed to investigate rates of later switching to mania.
Subsyndromal bipolar disorder has been described in 6% of adolescents in the community, but a longitudinal assessment showed that none of the adolescents with subsyndromal mania met criteria for full-blown bipolar disorder type I in their early 20s . In the study on Amish children , the presence of episodic miniclusters of increased and decreased energy, decreased sleep and anger/temper were considered the more typical prodromal manifestation in children at higher risk for bipolarity. The nature and the natural history of these subsyndromal forms, both subcontinuous and episodic, deserve further research.
It has been hypothesized that bipolar offspring show deficits consistent with the syndrome of nonverbal learning disabilities (NLD) . A recent test of this hypothesis showed that children at risk for bipolar disorder have a significantly higher verbal IQ than performance IQ, as well as psycho-motor deficits, but academic deficiencies in mechanical arithmetic relative to reading and spelling abilities, typical of NLD, were not demonstrated . Whether these cognitive abnormalities are predictive of the development of bipolar disorder is still unclear, even though they are similar to those found in adults with bipolar disorder .
Duffy et al.  explored whether some significant symptoms of inattention were present among the 53 offspring of 30 bipolar patients, with (n = 24) or without (n = 29) psychopathologies (mostly in the mood and/or anxiety domain). A lack of evidence of premorbid ADHD and an absence of current attentional problems was found with an objective measure (a cancellation test), even though with a subjective measure (a self-administered ADHD rating scale) a significant difference was found between the well and psychiatrically ill, as well as between those with and those without an affective disorder. This led to the hypothesis that attentional difficulties may reflect the activity of the underlying mental disorder rather than a real attentional problem, and caution against a possible overdiagnosis of ADHD in the presence of another Axis I disorder.
A dimensional approach can help to define behavioural and emotional profiles in children and adolescents of bipolar parents, capturing earlier manifestations of the disorder even before a categorical diagnosis. One example of this approach is the CBCL , a format reporting the behavioural and emotional problems of children (4-18 years) as described by parents. Dienes et al.  reported higher scores on all the CBCL scales in bipolar offspring. Within these offspring, subjects with a diagnosable mental disorder (bipolar disorder, ADHD, depression and/or anxiety) scored significantly higher than those without a clinical disorder on numerous CBCL subscales. The offspring with bipolar disorder were more pervasively disturbed than the rest of the clinical portion of the sample, even though several scales did not distinguish the bipolar disorder and ADHD groups. Furthermore, ADHD and depressed/anxious children did not differ as well at the CBCL. These findings led to the suggestion that a prodromal-subclinical bipolar disorder in ADHD and depressed/anxious children of bipolar parents (as well as in nonclinical bipolar offspring) may have determined higher scores at the CBCL, compared to non-bipolar offspring.
Kochman et al.  demonstrated that, among adolescents with major depression, trait cyclothymia with extreme lability was a predictor of suicide attempts in a 2-year prospective follow-up, as well as of the development of bipolar disorder. Such data underscore the immense public health importance of the foregoing treatment efforts.
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