ADHD is more commonly diagnosed in boys than in girls, but this may be partly due to differences in how symptoms present and how the diagnostic process was developed.
Girls with ADHD often “fly under the radar” and are underdiagnosed because they are more likely to show inattentive symptoms, such as difficulty concentrating, rather than the hyperactive and impulsive behaviours that are more typical in boys.
Girls also tend to display more internalising symptoms, such as anxiety and depression, whereas boys are more often characterised by externalising behaviours like hyperactivity, impulsivity, and oppositional conduct.
As a result, the inattentive and internalising symptoms often seen in girls are more likely to lead to a diagnosis of anxiety or depression instead of ADHD.
In contrast, the more disruptive behaviours seen in boys often prompt the ADHD diagnostic process.
Another contributing factor is that the current diagnostic criteria for ADHD were originally based on studies of boys, meaning the way ADHD is assessed is more tailored to how it typically appears in boys rather than in girls.