The holy grail of ADHD diagnosis is to have a test that tells you objectively, with no margin of error: yes, this person has ADHD or no, they dont. We dont have that yet, but we do have neuropsychological tests, which tell you something about how a persons brain works.
A more complicated question is what, exactly, neuropsychological testing tells you. Is it possible to accurately diagnose ADHD based purely on neuropsychological tests?
The details vary from test to test, but in general the answer is no. Neuropsychological test results are one type of data that an experienced clinician will use in combination with questionnaires, interviews, and other tools to make an informed diagnosis.
To see why neuropsychological tests for ADHD are useful but also limited, consider a recent study on the Cambridge Neuropsychological Test Automated Battery, a set of tests known less tongue-twistingly as CANTAB.
The study found that CANTAB does identify executive functioning disorder fairly reliably. In other words, if you have impairments with things like planning, memory, attention, inhibition, processing speed and so on, the tests will likely pick that up.
And the study also confirmed that people with ADHD tend to have impairments in those areas. But the problem is that people can have deficits in those areas for plenty of other reasons, such as a different mental health or brain condition. In other words, the tests will tell you whether you have executive functioning impairments, but they wont tell you whether those impairments are because of ADHD.
There are some neuropsychological tests designed to assess ADHD specifically. But even then the results arent clear-cut.
One popular neuropsychological test for ADHD is the TOVA, where the person taking the test has to watch and press a button whenever a certain shape appears. However, research suggests that intelligence can skew some of the tests effects, with more intelligent children getting more false negatives.
All of which is to say that neuropsychological tests are informative, but they dont provide conclusive diagnostic answers by themselves. A good doctor will use these tests in conjunction with other information and look at the big picture to make diagnosis.
Image: Flickr/Ivo Dimitrov