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J Affect Disord. 2015 Oct 1;185:123-8. doi: 10.1016/j.jad.2015.06.018. Epub 2015 Jun 23.

Conversion from depression to bipolar disorder in a cohort of young people in England, 1999-2011: A national record linkage study.

Author information

1
Highfield Unit, Warneford Hospital, Oxford OX3 7JX United Kingdom. Electronic address: anthony.james@psych.ox.ac.uk.
2
Unit of Health-Care Epidemiology, Nuffield Department of Population Health, University of Oxford, Old Road Campus, Oxford OX3 7LF United Kingdom.
3
Department of Psychiatry, Mathison Centre for Mental Health Research and Education, Hospital Drive NW, Calgary, AB, Canada T2N.

Abstract

OBJECTIVE:

To estimate the conversion rate from unipolar depression (ICD10 codes F32-F33) to bipolar disorder (BP) (ICD10 codes F31) in an English national cohort. It was hypothesised that early-onset BP (age <18 years) is a more severe form of the disorder, with a more rapid, and higher rate of conversion from depression to BP.

METHOD:

This record linkage study used English national Hospital Episode Statistics (HES) covering all NHS inpatient and day case admissions between 1999 and 2011.

RESULTS:

The overall rate of conversion from depression to BP for all ages was 5.65% (95% CI: 5.48-5.83) over a minimum 4-year follow-up period. The conversion rate from depression to BP increased in a linear manner with age from 10-14 years - 2.21% (95% C: 1.16-4.22) to 30-34 years - 7.06% (95% CI: 6.44-7.55) (F1,23=77.6, p=0.001, R(2)=0.77). The time to conversion was constant across the age range. The rate of conversion was higher in females (6.77%; 95% CI: 6.53-7.02) compared to males, (4.17%; 95% CI: 3.95-4.40) (χ(2)=194, p<0.0001), and in those with psychotic depression 8.12% (95% CI: 7.65-8.62) compared to non-psychotic depression 5.65% (95% CI: 5.48-5.83) (χ(2)=97.0, p<0.0001).

LIMITATIONS:

The study was limited to hospital discharges and diagnoses were not standardised.

CONCLUSIONS:

Increasing conversion rate from depression to bipolar disorder with age, and constant time for conversion across the age range does not support the notion that early-onset BP is a more severe form of the disorder.

KEYWORDS:

Bipolar disorder; Conversion; Depression

PMID:
26172983
DOI:
10.1016/j.jad.2015.06.018
[Indexed for MEDLINE]

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