Attention Deficit Hyperactivity Disorder in GirlsDR S M AHMAD, MRCPsych
Consultant Child and Adolescent Psychiatrist
DR D ANDERSON, MRCPsych
Staff Grade Old Age Psychiatry
Attention deficit hyperactivity disorder is the most commonly diagnosed neuro-behavioural disorder. It is now increasingly recognised that ADHD is a life-span condition that can have a devastating impact on the daily lives of individuals and their families. Early diagnosis and appropriate treatment are paramount for a better prognosis. Without prompt intervention consequences such as anti-social behaviour, aggression, poor self-esteem, alcohol and drug problems and self-harm can occur during the developmental trajectory into adulthood. It is well recognised that most of the focus has been on hyperactive boys and girls with ADHD are under-recognised, under-diagnosed and under-treated (Biederman et al, 2005). There are millions of females worldwide with ADHD who are suffering silently and represent a major public health concern. The prevalence of ADHD in children is between 8-10% and declines in adulthood to 2-3%. In terms of female prevalence out-patient samples estimate it to be between 6:1 and 9:1, with community samples at 3:1 (Gaub and Carlson, 1997).
Recent work to examine gender differences proposes that these differences are not due to actual phenotypic variation but due to bias in those referred. Few studies, as identified in the meta-analysis of Gaub and Carlson, included sufficient numbers of females. It has been hypothesised that such apparent differences may be due to the referral source. Work on clinic-referred samples does not seem representative of the population of ADHD in girls, when compared to non-referred samples. ADHD does present commonly in girls but not as frequently as boys. Its presentation is subtly different to the classic description given to boys. In non-referred samples they tend to show lower levels of hyperactivity, fewer conduct problems and lower levels of externalising behaviour (Gaud and Carlson, 1997).
Most diagnostic criteria were originally formulated from predominantly male cohorts (Rielly et al, 2006). Such research has been overshadowed by the phenotypic expression in boys of hyperactivity and impulsivity. Gender specific variations influence clinical practice in a way that may adversely affect the recognition of ADHD in girls. Boys tend to present with symptoms such as hyperactivity, externalising behaviour, oppositional and defiant behaviour, verbal and physical aggression and substance misuse. Girls however present with inattention, internalising behaviour, leisure time and opposed to classroom impairment, anxiety and depression, lowering of self-esteem and feelings of guilt (Rielly et al, 2006). Most differences between genders tend to be small, but seemingly the most common symptoms in boys are “easily distracted” and “hyperactive” and with girls the most common symptom is “difficulty sustaining concentration”. It may be that referral bias is skewing results as some differences are mediated by referral source (Gaud and Carlson, 1997).
It has further been noted in parenting styles between genders that mothers of ADHD boys tend to be less authoritarian compared to mothers of girls and this may also affect the threshold for referral (Rielly et al, 2006). Another potential skew may arise from teachers. It has been suggested that teachers under-recognise inattention in girls, perhaps due to the greater impact of hyperactive behaviour often shown by boys upon the classroom. Several other potential factors have been hypothesised including comorbidity, developmental problems, diagnostic procedures and the effects of rater source (Gaub and Carlson, 2006).
These differences may lead to differing treatment styles. It can be hypothesised with boys that psychosocial interventions focusing more on aggression and with girls focusing more on anxiety might seem sensible. Parent training with girls might also aim to improve inattention but with boys such training might focus on hyperactivity and disruptive behaviour. Management plans may also need to take into account likely prognoses. Girls seem to have a higher risk of adult psychiatric admission than boys and comorbidity with conduct disorder may increase this risk (Dalsgaard et al, 2002). Further research into the reasons for this may create particular emphases in management during adolescence. Adolescent girls also seem more likely to present with personality disorder, which again will require particular attention in assessment and management (Burkett et al, 2005). Otherwise few differences between genders exist with regards to comorbidities during childhood (Biederman et al, 2005). Girls do not differ from boys in response to methylphenidate and dextroamphetamine (Sharp et al, 1999).
The neglected status of gender-differences in ADHD raises a number of questions, for example can diagnostic criteria inferred from studies of boys be routinely applied to girls with ADHD? Without a better understanding of the aetiology of these differences it is impossible to determine if diagnostic criteria in DSM-IV and ICD-10 are fully valid for girls. Despite a recent focus on gender differences in the clinical presentation of ADHD the disorder remains a hidden morbidity in girls and is associated with significant functional impairment across a life-time. It appears that attributional errors and personal prejudices on the part of parents, teachers and clinicians hinder recognition and treatment. In clinical practice out-patient referred ADHD girls are generally not representative of ADHD girls. It does seem that only the most severely affected girls are being referred for treatment and the majority of ADHD girls suffer silently. ADHD in both genders is associated with high levels of psycho-educational impairment. There is an urgent need for appropriate epidemiological studies examining gender differences in ADHD. There should be increased emphasis on education and training of clinicians, teachers and parents to spot symptoms in girls with ADHD.
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