Antidepressant use among individuals registered for the Public Prescription Drug Insurance Plan in Québec – descriptive study from 1999 to 2004 (only available in French)

The use of antidepressants is increasing and approved and non-approved indications for these drugs are multiplying. In recent years, however, Health Canada has published a number of notices and warnings about these drugs, one of which, nefazodone, has even been discontinued. Following the recommendations of the Table de concertation du médicament, the Conseil du médicament chose the study of antidepressant usage in Québec as one of its top priorities. 

The Conseil analyzed the prevalence of antidepressant use among those registered for the Public Prescription Drug Insurance Plan administered by the Régie de l’assurance maladie du Québec (RAMQ) between 1999 and 2004. The analysis studied annual cohorts of individuals who had ongoing coverage between January 1 and December 31 of any one year between 1999 and 2004. Data for 2005 and 2006 were added in Appendix 1 of the report. Analyses were also conducted on two cohorts of individuals insured during five consecutive years either between 1999 and 2003 or between 2000 and 2004. Lastly, in order to study use by new users, cohorts of individuals insured during three consecutive years were also formed in order to obtain their antidepressant usage during the year preceding and the year following the year studied. The use of other types of drugs for the treatment of central nervous system disorders among antidepressant users was also examined.

Antidepressant usage climbed from 8.1% in 1999 to 10.6% in 2004. The average annual duration of antidepressant use per individual rose from 226.0 days in 1999 to 281.9 days in 2004. Between 2000 and 2004, nearly one in five people (19.2%) took antidepressants for at least one of the five years, whereas one person in twenty (5.2%) took antidepressants during each of those five years. Use is more prevalent among women than men. Use is also more prevalent among employment assistance recipients than among the employed, and generally increases with age.

Among those individuals who received at least one diagnosis of major depression over the course of a year, 68.5% received antidepressants in 2004, up from 67.2% in 1999. In the case of those individuals affected by anxiety disorders, these rates were 41.5% and 35.9% respectively. While it is generally recommended that individuals suffering from major depression take antidepressants for at least nine months, only 36.4% of new users in 2003 followed treatment for this amount of time.

Notable changes were observed between 1999 and 2004 as to the common denominations of the most frequently used antidepressants. Relative to overall prescriptions, the proportion of prescriptions for citalopram and venlafaxine doubled, while those for paroxetine and sertraline fell by more than half and those for amitriptyline remained steady.