qEEG vs Questionnaire: Which ADHD Assessment Actually Measures Your Brain?

If you've ever taken an online ADHD quiz and seen "likely ADHD" flash across your screen, you've used a questionnaire. If you've sat in a GP surgery while your doctor ticked boxes on a Conners scale, you've used a questionnaire. If your child's teacher has filled out a Vanderbilt form rating their classroom behaviour from 0 to 3, that's a questionnaire too.

Questionnaires dominate ADHD assessment in the UK. They are cheap, fast, and require no specialist equipment. They are also subjective, biased, context-dependent, and they do not measure your brain.

There is another way. Quantitative EEG — qEEG — places sensors on your scalp and measures the electrical activity of your brain directly. No opinions. No rating scales. No "how often does your child fidget?" Just data.

This article compares both approaches honestly, including the limitations of each, so you can decide what kind of evidence you actually want.

Two fundamentally different approaches

At the most basic level, questionnaires and qEEG answer different questions.

A questionnaire asks: "What does this person's behaviour look like to an observer?" It captures reported symptoms — fidgeting, difficulty concentrating, losing things, interrupting. The answers come from a person (self-report) or someone who knows them (parent, teacher, partner). The data is inherently filtered through human perception, memory, and interpretation.

A qEEG asks: "What is this person's brain actually doing?" It measures cortical electrical activity — the theta/beta ratio, frequency band power, and attention task performance. The data comes from the brain itself, not from anyone's opinion about what the brain might be doing. It cannot be influenced by mood, motivation, social pressure, or how much sleep someone had last night.

Neither is "wrong." They measure different things. But only one measures the organ that ADHD actually affects.

How questionnaires work — and where they fail

The most widely used ADHD questionnaires in the UK are the Conners scales (parent, teacher, and self-report versions), the Vanderbilt Assessment Scales, the SNAP-IV, and the ASRS (Adult ADHD Self-Report Scale). All follow a similar format: a list of behavioural statements rated on a frequency scale — "never," "sometimes," "often," or "very often."

These instruments were developed through decades of clinical research and they do capture real behavioural patterns. A child who scores highly across multiple Conners subscales from both parent and teacher raters probably does have attention difficulties. The sensitivity of well-administered questionnaire batteries is typically quoted at 70-85%.

But 70-85% means that 15-30% of people with ADHD are missed. And the reasons they're missed reveal the fundamental weaknesses of the questionnaire approach.

The problems with questionnaires

There's one more problem that's rarely discussed: questionnaires cannot distinguish between conditions that look similar. A child with anxiety, trauma, sleep deprivation, or a processing disorder can score highly on an ADHD questionnaire because the behavioural presentation overlaps. Inattention is a symptom of many conditions, not just ADHD. Questionnaires see the symptom. They cannot see the cause.

How qEEG works — measuring the brain directly

Quantitative EEG takes a completely different approach. Instead of asking about behaviour, it measures brain activity directly using sensors placed on the scalp.

The key measurement for ADHD is the theta/beta ratio (TBR) — the balance between slow-wave theta activity (4-8 Hz, associated with unfocused, daydreaming states) and fast-wave beta activity (12-30 Hz, associated with focused concentration). In ADHD, this ratio is consistently elevated. The brain produces too much theta relative to beta — the cortex is under-aroused even when the person is actively trying to concentrate.

This isn't a new or experimental measurement. The theta/beta ratio has been studied for over 30 years across hundreds of independent research papers. The FDA referenced it when clearing the NEBA System in 2013 as a diagnostic aid for ADHD in children aged 6-17. Our screening measures the same biomarker, at the same cortical site (Cz), compared against a normative database built from six peer-reviewed sources covering 311 research subjects.

In addition to the resting-state brain data, a Go/No-Go attention task provides behavioural metrics that are quantified rather than observed: sustained attention (hit rate), impulse control (false alarm rate), attention lapses (miss rate), and cognitive consistency (reaction time variability). These are the same constructs that questionnaires try to capture through subjective rating, but here they are measured directly and expressed as numbers.

Results are reported as z-scores — standard deviations from the age-matched mean. A z-score of 2.0 means the measurement sits 2 standard deviations above the norm for that age group. No interpretation required. No observer. No bias. Just a number compared against published research.

Side-by-side comparison

The bias problem questionnaires can't solve

The bias issues aren't theoretical. They have real consequences for real people.

Research consistently shows that boys are rated as more hyperactive than girls on teacher questionnaires, even when objective measures show identical levels of activity. Girls with ADHD are systematically under-identified because their presentation — quiet daydreaming rather than disruptive bouncing — doesn't trigger the same observer responses.

Adults face a different bias problem: self-report accuracy degrades with age. An adult who has spent 30 years developing compensatory strategies may not recognise their own symptoms as abnormal. They think everyone loses their keys five times a week. They think everyone rereads the same paragraph twelve times. They've normalised their own struggle, and a questionnaire that asks "how often do you..." gets answers calibrated to a distorted baseline.

Cultural bias adds another layer. Rating scales developed in American research contexts may not translate cleanly to British, South Asian, or Caribbean cultural norms around child behaviour, attention expectations, and what counts as "often" versus "sometimes."

Why the best approach uses both

We're not arguing that questionnaires are useless. They capture important information about how ADHD manifests in daily life — context that brain data alone doesn't provide. A theta/beta ratio doesn't tell you whether a child is struggling more in maths or English. A teacher questionnaire does.

Research from the American Academy of Neurology found that combining theta/beta ratio data with standard clinical evaluation improves ADHD diagnostic accuracy to 89-94% — significantly higher than either approach alone. The brain data provides the neurological evidence. The clinical interview and questionnaires provide the behavioural context. Together, they give the most complete picture.

But here's the practical reality in the UK: getting the clinical interview part requires a CAMHS referral (2-5 year wait) or a private psychiatrist (£700-£1,500). The brain data part is available this week for £595, with a same-day report that your GP can use to fast-track the clinical part.

For many families, the qEEG screening is the catalyst that starts the whole process. It provides the objective evidence that turns "we suspect ADHD" into "the brain data shows a pattern consistent with ADHD" — and that shift in language changes how quickly the system responds.

Who gets missed by questionnaires alone?

If you recognise yourself or your child in any of these descriptions, questionnaires may not capture the full picture:

Women and girls with predominantly inattentive ADHD. Quiet, compliant, daydreamy. Teachers rate them as "shy" not "ADHD." Their brain data often tells a very different story.

High-IQ children who compensate through intelligence. They score well academically despite enormous internal effort. Questionnaires see the grades. Brain data sees the cortical under-arousal that makes those grades cost ten times more energy than they should.

Adults diagnosed with anxiety or depression who were never screened for ADHD. The inattention was attributed to their mood disorder. SSRIs helped the anxiety but the focus problems persisted — because the underlying cause was never identified.

People from cultural backgrounds where ADHD awareness is lower and behavioural expectations differ. Questionnaires calibrated to Western norms may not capture presentations that are shaped by different cultural contexts.

Anyone who has learned to mask their symptoms so effectively that they no longer recognise them. You can mask behaviour. You cannot mask brain activity.

Common questions

Related: The science behind qEEG · How the screening works · Understanding your results · ADHD in women · Pricing