Use of ICD-10 diagnoses in Danish psychiatric hospital-based services in 2001-2007.

The Danish version of the ICD-10 chapter on mental and behavioural disorders has 380 different diagnoses when three digits are used. This study examines how many of the available diagnoses were used and to what extent in Danish psychiatric hospital-based services in the period from 2001 to 2007, through an analysis of the total number of diagnoses reported to the Danish Psychiatric Central Research Register (n=1,260,097). The 50th percentile (50.1%) was reached by using 16 diagnoses (4.2% of 380 available). The three most frequently registered diagnoses were paranoid schizophrenia, alcohol dependence and adjustment disorder, used 10.2%, 8.3% and 5.9% of the times, respectively. Seven diagnoses (1.8%) were used between 1 and 4 times during the 7-year period. One hundred nine (28.7% of available diagnoses) were used less than 100 times each. These data suggest that it may be sensible to reconsider the number of diagnoses needed in the revision of the ICD-10 chapter on mental and behavioural disorders.