ONSET

The first symptoms of this illness are often recognized in childhood or adolescence but more classic presentations of MDI are most common in early adulthood. It is rare to observe the onset of MDI in late life unless earlier episodes went undiagnosed or a medical condition contributes to its onset. (McDonald)

In a study of age at onset in 211 patients with DSM IV Bipolar Disorder (BD), Bellivier et al. reported a distribution of cases consistent with different ages of onset. In this study, age of onset was defined as the age when DSM IV criteria were first met for either depression or mania. In 41.4% of the population studied, this occurred at 16.9 years.

In a survey of 500 adults diagnosed with Bipolar Disorder, the age of onset of mood symptoms was traced to age 19 or less by 59% of responders (17% before 10 years of age and 14% before 14 years). Those with early onset had (statistically significant) higher rates of family history of BD, greater rates of High School dropout and financial difficulties, divorce and marital difficulties, more alcohol and substance abuse, more injuries to self and to others, and more recurrences.

It is estimated that 60% of the children with manic/hypomanic symptoms only meet criteria for Bipolar Disorder NOS, as they do not satisfy the episode duration requirement. (Geller)

Pediatric precursors of MDI are not always symptoms or manifestations of adult MDI. Depressive symptoms including tearfulness, self-loathing, lack of interest and social withdrawal are often combined with prominent anxiety symptoms with a characteristic tendency to wax and wane, confusing parents and clinicians alike. The variability of clinical presentation and the intermittent course of illness often lead parents and clinicians to disregard or minimize the significance of the symptoms. Often, multiple diagnoses are given as Symptoms change over time or due to the emphasis given by different clinicians to different symptoms. Only the prolonged follow-up of these cases confirms the common cause of these manifestations, especially when more classic symptoms of MDI begin to appear.

Childhood onset is often subtle with temper tantrum and other mood symptoms combined often with intense separation anxiety or phobic, panic and OCD symptoms. Depressive symptoms in a prepubertal child should always be regarded with suspect, as a high percentage of prepubertal children with depressive episodes will experience Mania or Hypomania in the course of their illness, either spontaneously or following treatment with antidepressants.

In childhood MDI, the episodes are short and very frequent. The variability of the behavioral manifestations can lead to misdiagnosis and inadequate or inappropriate treatment.

Adolescent forms of MDI are common, possibly due to:
 Expression of genetic vulnerability increases with age;
 Destabilizing effect of hormonal changes at puberty;
 Increased use of alcohol and other drugs.

Adolescent-onset MDI might be more similar to adult-onset than forms with prepubertal onset. The high rate of comorbid diagnoses and low compliance with treatment are complicating factors in diagnosing and treating MDI in adolescence.

Late-onset MDI remains fairly uncommon and the presence of medical or neurological conditions is often a contributing factor, if not a cause for manic syndromes in the elderly. In many cases, however, the onset of MDI dates back many years. Earlier episodes might have gone undiagnosed and untreated, and give the impression that the illness has onset late in life.