A three-country comparison of psychotropic medication prevalence in youth

Aims of the study

The study aims to compare psychotropic drug use cross-nationally among 3 Western countries. The outcome data presented for the year 2000 were the prevalence of stimulant, antipsychotic and antidepressant medication and any psychotropic use in youth aged 0–19 years from 2 major European countries and the US. Drug class data from each country were compared with respect to total prevalence and were stratified by age and gender.

Data sources

Measures

Annual prevalence was defined as the dispensing of 1 or more prescriptions for a psychotropic drug during the study year (2000) per 100 enrolled youth. Prevalence was stratified by age and gender. Nine classes of psychotropic drugs included: antidepressants, antipsychotics, alpha-agonists, anxiolytics, hypnotics, lithium, antiparkinsonian agents, anticonvulsant-mood stabilizers and stimulants. Antidepressant subclasses included selective serotonin reuptake inhibitors (SSRI), tricyclic antidepressants (TCA) and other antidepressants. Antipsychotic subclasses included atypical and conventional antipsychotics. Stimulants included methylphenidate and amphetamine products. Anticonvulsant-mood stabilizers (ATC-MS) included carbamazepine, divalproex/valproic acid, lamotrigine, gabapentin and topiramate. Cross-national comparisons of any psychotropic medication use presents a challenge, in that anticonvulsant-mood stabilizers are used far more commonly in the US for psychiatric purposes than in Europe. Unfortunately, the study data did not have diagnoses available on indications for their use. Consequently, to improve the validity of anticonvulsants for mood stabilizer use, we restricted the analysis to ATC-MS users who additionally had one or more psychotropic classes in the study year, thereby excluding those most likely to receive these medications for the treatment of seizure disorder. Concomitant drug use refers to combinations of medications used concurrently and the analysis compared monthly combination drug dispensing within 3 time frames: 1 year, 3 months and 1 month, to assess the effect of each time frame on the prevalence of co-prescription. As in the prevalence of any psychotropic medication use, concomitant use with ATC-MS data was adjusted by excluding individuals who had ATC-MS dispensed but no other psychotropic medications during the study year.

Analysis

The cross-sectional analysis describes the total, age-and gender-specific prevalence across three countries. The age and gender distributions of the enrolled youth (denominator) were adjusted applying the direct standardization method and using the 2000 US census population estimates as the standard population [16]. This adjustment corrects for the imbalanced age distribution caused by the US data with its higher proportion of 0–4 year olds and permits fair comparison across countries. Annual prevalence and the 95% confidence intervals (Cls) estimated by the exact method [17] are presented. Confidence intervals at the 95% level for these standardized total estimates were obtained by the Chiang method [18]. Prevalence ratios were calculated to compare countries and the 95% CIs for ratios were based on the method of Dawson and Trapp [19]. The frequency of concomitant use was calculated and the highest ranking combinations were assessed for each country.

Prevalence findings

In Germany and the Netherlands, 15–19 year olds were over 3 times more likely to utilize antidepressants than 10–14 year olds, whereas in the US the 15–19 year old group use was only 28% higher than in the younger aged group. In the US, only 14.8% of those on antidepressants were prescribed the TCA antidepressant subclass, whereas the proportion for TCAs was 48% in the Netherlands and 73% in Germany.

Concomitant psychotropic patterns

To assess concomitant therapy in 3 time frames, 1-month (April 2000), 3-month (April through June) and 12-month time periods were used to measure the one-month co-occurrence of psychotropic classes for youth in the US dataset. There was a linear increase in co-occurring use as the time period widened: 19.2%, 23.9% and 27.0%. For the present study, the most conservative approach, (monthly co-occurrence) was adopted to avoid exaggerated estimates. Combinations were assessed from the following classes: stimulants, antidepressants, anxiolytics/hypnotics, alpha-agonists, antipsychotics, anticonvulsant-mood stabilizers and lithium. Of the 1908 medicated youth in the US group, concomitant therapy (defined as monthly co-occurrence) applied to 19.2% and ranged from pairs (n = 279), triplets (n = 80), quadruplets (n = 7) to 6 drug classes (n = 1). The leading pairs were stimulants with antidepressants (33.7%) and stimulants with alpha-agonists (18.3%). Dutch concomitant use was substantially less common: 8.5% had combined therapy almost entirely as pairs (77/80), of which stimulants and antipsychotics were the leading combination. German concomitant use affected only 5.9% of medicated youth and the use was entirely pairs except for one triplet. Since the bulk (62%) of the German combinations involved anticonvulsant-mood stabilizer and an anxiolytic/hypnotic, it is not possible to determine the extent of seizure disorder treatment. The other German pairs were ranked as follows: stimulant and antipsychotic (8.9%), anticonvulsant-mood stabilizer and antipsychotic (7.6%) and stimulant and anticonvulsant-mood stabilizer (6.3%). Concomitant use with anticonvulsant-mood stabilizers affected 5.8% (110/1908) of US medicated youth, 1.9% (18/937) of medicated Dutch youth and 4.6% (62/1358) of medicated German youth.

Broad cross-national trends

In a review of 10 Medline reports of published studies of prevalence of psychotropic medications prescribed for youth in Western European countries during the period from 1999 to 2002, there was general agreement on their low rates of use of psychotropic medications in youth relative to published reports of US utilization [4, 20–29]. Stimulant prevalence was particularly low in France (0.05%) [20], but relatively higher (1.0%) in the Netherlands. Consistent with previous findings, antidepressant use is more common in the US. In a four-country antidepressant analysis, use of more than one antidepressant during the year 2000 was approximately four times more frequent in US youth (21.3%) than in Dutch (5.9%), German (5.4%), and Danish (5.6%) youth [27]. The striking antidepressant subclass pattern of the present study shows SSRIs represent nearly two-thirds of antidepressant use in US and Dutch youth, but less than one-quarter of German antidepressant use. The prevalence of antipsychotics in youth aged 0–4 ranged from 0.13% in Italy [24] to 0.5% in the Netherlands [29]. Generally, these antipsychotic prevalence findings closely matched those of this study, indicating that US youth -compared to Western Europeans-have a far higher prevalence of stimulants and antidepressants, but a less disparate prevalence of antipsychotics. Patterns for less commonly used psychotropic medications were remarkably similar across the 3 countries for lithium, alpha-agonists and antiparkinsonian agents but Dutch usage led the other countries in anxiolytic and hypnotic use. In the following sections, several factors that influence the utilization of psychotropic drugs across countries are presented.

Regulatory differences

Amphetamines are seldom prescribed in Western Europe. In fact, they were not allowed to be prescribed in France [20, 30], Spain [31], and Italy [30], at the time of this study. Government cost restrictions in Europe have also cut down on the use of expensive drugs, particularly with respect to patent-protected antipsychotics and antidepressants [1, 32]. These year 2000 patterns may be expected to change as recent European data suggest [30].

Diagnostic classification differences

The International Classification of Diseases (ICD-10) is now generally used for diagnostic purposes in Western Europe. This fact can influence the frequency of diagnosis and through that to treatment. For example, the diagnosis of hyperkinetic disorder in the ICD is more stringent than that of attention deficit hyperactivity disorder (ADHD) in the US based on the Diagnostic and Statistical Manual (DSM) criteria [33, 34]. However, there is evidence that conduct disorder is more readily diagnosed in the UK using the ICD than in the US with the DSM [35]. The US trend of increasing bipolar diagnosis in children and adolescents [36] does not reflect European practice [37].

Drug class preferences

The common use of phenothiazine products in German youth aged 0–4 may be due to its medical usage for antihistaminic effects or to induce sleep, and not for psychiatric indications. In the US, several phenothiazines, e.g. promethazine, have antihistaminic properties which have been used to treat allergy and cold symptoms, but these drugs are classified separately and were not assessed as psychotropic uses. That may not be the case in Europe. Similarly, in Sweden during the late 1970s and early 1980s, 10% of youth had received prescriptions for neuroleptic drugs before their 5^th birthday for sedative/hypnotic use [38]. The use of antidepressants varies by physician specialty depending on the setting and type of insurance. In year 2000, the prevalence of prescribed stimulant medication for 0–4 year-olds in Western Europe was quite low [UK (0%), Germany (0.02%), Netherlands (0.05%)] in relation to the US (0.49%) [39].

Co-medication patterns

Use of multiple medications, i.e., having two or more prescribed psychotropic medications during a one year period, was rare in the Netherlands in 1999 compared to the US [21]. In the current study, US concomitant use was 2 or 3 times more common than in Dutch and German youth, respectively.

Access to physician specialties

General practitioners prescribe most of the psychotropic drugs in Western Europe. In the US, pediatricians prescribe most of the stimulants for youth [40], whereas psychiatrists prescribe most of the antipsychotics [41]. In France, the first prescription of a stimulant must be written by a specialist. The general practitioner can continue stimulant prescribing, but only for a maximum period of one year [20]. The number of child psychiatrists per capita in Western Europe is low compared to the rate in the US [35], which presumably also accounts for some prescribing differences.

Limitations

Several limitations should be noted: 1) These data are cross-sectional in nature, covering one year, which do not permit time trend analyses. Future studies should address changing patterns over time. 2) Diagnostic information was not available so that it is unclear if antidepressants were prescribed for depression, anxiety, obsessive compulsive disorder or other indications. 3) US direct-to-consumer prescription drug advertising and professional journal advertising may contribute to increased awareness and utilization of medication to treat emotional and behavioral conditions in children. 4) There is no information on reimbursement patterns. 5) Access to medical specialists differs. 6) The US data were based on the s-CHIP Medicaid data from one state and have limitations as a representative US dataset, but adjustments were made to improve generalizability, e.g. prevalence of use rates were adjusted for the greater proportion of 0–4 year-olds in s-CHIP. 7) The analysis of the major psychotropic drug classes in this study did not include certain commonly used over the counter (OTC) drugs that are not generally recognized as important. Examples include St. John's Wort–used prominently in Germany for the treatment of depression [1] and the extensive use of anxiolytics and hypnotics for adolescents in many European regions [22].