Cognitive Disengagement Syndrome (CDS) and ADHD: Mental Fog, Daydreaming and Inattention
Do you frequently zone out, daydream or stare into space? Does your brain sometimes feel foggy, slow or disconnected, even when you are trying to concentrate? Are you slowed down rather than sped up?
These experiences can occur in ADHD, particularly with difficulties with attention. However, researchers have identified a cluster of symptoms that appears to overlap with ADHD but is not quite the same. This is known as Cognitive Disengagement Syndrome (CDS).
You may have previously heard the term “sluggish cognitive tempo” (SCT). This older term is now being replaced by CDS because it was felt to be potentially misleading and judgemental.
Importantly, CDS is not currently a formal diagnosis and is not an ADHD presentation. It is an emerging research construct that may help us understand a particular pattern of cognitive and behavioural difficulties.
What is Cognitive Disengagement Syndrome?
CDS describes experiences such as:
Frequent daydreaming or getting lost in thought
Staring into space
“Zoning out”
Mental fog or confusion
Losing your train of thought
Difficulty finding the right words
Feeling that your thinking is slow
Taking longer to process information
Feeling sleepy or mentally tired
Low energy
Difficulty getting started with activities
Moving or responding more slowly
These experiences can occur occasionally for anyone. CDS research focuses on persistent difficulties that are frequent enough to affect everyday functioning.
Someone might describe it as:
“I wasn't distracted – I just wasn't there.”
Or:
“I was looking at the page, but none of it was going in.”
Is CDS the same as ADHD?
No, although there is significant overlap.
Research suggests that CDS is particularly associated with ADHD inattentive symptoms, but the two appear to be distinguishable.
ADHD inattention can involve being easily distracted, making careless mistakes, struggling with organisation, losing things, forgetting tasks and finding it difficult to sustain attention.
CDS is more strongly associated with daydreaming, mental fog, staring into space, cognitive disengagement, slowed thinking and low energy.
The distinction isn't always straightforward. Someone with ADHD may absolutely describe themselves as “spaced out” or prone to daydreaming.
The important point is that not every experience of poor concentration necessarily reflects ADHD.
Can you have CDS without ADHD?
Yes.
Research suggests that some people with prominent CDS symptoms do not meet criteria for ADHD. CDS has also been associated with anxiety, depression, sleep difficulties and social or academic difficulties.
This is one reason it is important not to assume that mental fog, tiredness or daydreaming automatically means someone has ADHD.
A comprehensive assessment considers the whole pattern of difficulties, their developmental history and other possible explanations.
Can you have ADHD and CDS?
Yes.
Someone can meet criteria for ADHD and also have prominent characteristics associated with CDS.
For example, a person with ADHD might experience significant distractibility and disorganisation but also describe a separate experience of becoming absorbed in their thoughts, staring into space or feeling mentally foggy.
Thinking about these experiences separately can sometimes provide a more useful clinical formulation.
Instead of simply asking:
“Do you have problems concentrating?”
we can ask:
“What actually happens when you find it difficult to concentrate?”
Are you distracted by everything around you? Or do you become mentally disengaged and lose track of what is happening?
Both can be described as “poor concentration”, but they may reflect different experiences.
What can CDS look like in everyday life?
At work
You might:
Read an email several times without taking it in
Lose track of meetings or conversations
Stare at your computer without starting a task
Take longer to process information
Find it difficult to get going in the morning
Need more time to respond to questions
At school or university
You might:
Daydream during lessons or lectures
Read material without remembering what you have read
Take much longer than expected to complete work
Struggle to maintain mental engagement
Find that you work better when someone helps you stay focused
In relationships
You might:
Lose track of conversations
Appear not to be listening
Miss parts of what someone has said
Frequently need people to repeat themselves
Become absorbed in your own thoughts
Importantly, this does not necessarily mean that you are uninterested.
You can be interested in something and still struggle to remain mentally engaged with it.
Could mental fog be caused by something else?
Absolutely.
Mental fog, poor concentration, tiredness and slowed thinking can have many possible causes, including:
Depression
Anxiety
Poor sleep
Sleep disorders
Stress and burnout
Trauma-related difficulties
Medication effects
Physical health conditions
Other psychological or neurodevelopmental difficulties
For example, someone experiencing depression may have low energy, reduced motivation and slowed thinking. Someone experiencing anxiety may find their attention repeatedly pulled towards worries.
This is why CDS should not be identified simply by ticking off a list of symptoms.
Is CDS a diagnosis?
Not at present.
Although research increasingly supports CDS as a recognisable symptom syndrome, it is not currently a formal DSM-5-TR diagnosis and is not one of the recognised presentations of ADHD.
Researchers are still considering how CDS should ultimately be classified. It may eventually be understood as a distinct disorder, a dimensional characteristic, a transdiagnostic syndrome, or something else.
For now, it is more accurate to talk about CDS characteristics or symptoms rather than saying that someone has been formally diagnosed with CDS.
Is there a treatment for CDS?
This is still an emerging area of research.
There have been relatively few studies specifically examining treatments for CDS. Some research has investigated whether medications used to treat ADHD may also affect CDS symptoms, but the evidence is currently limited and preliminary.
There is therefore no established medication specifically recommended for CDS.
Understanding the factors contributing to someone's difficulties – including ADHD, sleep, mood, anxiety and other psychological or physical health factors – is currently more clinically useful than assuming that CDS requires a particular treatment.
Why does CDS matter in an ADHD assessment?
The concept of CDS may help us develop a more detailed understanding of attention difficulties.
Two people can both say:
“I can't concentrate.”
But one may mean:
“Everything distracts me. I start one thing, notice something else and forget what I was doing.”
While another may mean:
“I don't really notice distractions. I just realise I've been staring into space for ten minutes.”
Both experiences can be impairing.
A thorough ADHD assessment therefore looks beyond whether someone has “poor concentration” and explores what their difficulties actually look like, when they occur, how long they have been present and what else might be contributing to them.
When should I seek an ADHD assessment?
If you have persistent difficulties with attention, organisation, impulsivity or activity levels, particularly if these difficulties have been present since childhood and are affecting your work, education, relationships or everyday life, an ADHD assessment may be helpful.
You may also want to seek an assessment if descriptions such as “daydreaming”, “zoning out”, “mental fog” or “not applying yourself” have been used to describe you, but you feel these explanations don't fully capture your experience.
An ADHD assessment should consider your developmental history, current functioning and possible alternative or additional explanations for your difficulties.
At ATH, we provide specialist adult ADHD assessments informed by current NICE and UK professional guidance.
Find out more about our adult ADHD assessments →
The bottom line
Cognitive Disengagement Syndrome is an emerging area of research, rather than an established diagnosis.
The research suggests that experiences such as daydreaming, zoning out, mental fog, slowed thinking and cognitive disengagement can overlap with ADHD but may also represent a distinct pattern of difficulties.
For someone undergoing an ADHD assessment, recognising these differences can help create a more nuanced understanding of their experiences.
And importantly, not every difficulty with concentration is ADHD – and not every difficulty needs to be explained by a single diagnosis.
The most useful assessment is one that considers the whole picture and asks not simply “Can you concentrate?”, but “What happens when you find it difficult to engage, concentrate or get started?”
References
Becker SP, et al. (2022). Report of a Work Group on Sluggish Cognitive Tempo: Key Research Directions and a Consensus Change in Terminology to Cognitive Disengagement Syndrome. Journal of the American Academy of Child & Adolescent Psychiatry. DOI: 10.1016/j.jaac.2022.07.821.
Rowe MA, et al. (2026). Investigating the Shared and Divergent Neuroanatomical Features of Attentional Deficits in Adolescents. Journal of the American Academy of Child & Adolescent Psychiatry. DOI: 10.1016/j.jaac.2025.05.006.
Becker SP, Leopold DR, Burns GL, et al. (2015). The Internal, External, and Diagnostic Validity of Sluggish Cognitive Tempo: A Meta-Analysis and Critical Review. Journal of the American Academy of Child & Adolescent Psychiatry. DOI: 10.1016/j.jaac.2015.12.006.
Burns GL, Becker SP, Montaño JJ, Servera M. (2024). Clinical Distinction Between Cognitive Disengagement Syndrome and ADHD Presentations in a Nationally Representative Sample of Spanish Children and Adolescents. Journal of Child Psychology and Psychiatry. DOI: 10.1111/jcpp.14005.
Becker SP, Martinez AC, Wiggs KK, Langberg JM, Smith ZR. (2023). Multi-method Examination of Cognitive Disengagement Syndrome and ADHD Inattentive Symptoms in Relation to Early Adolescents’ Academic Functioning. European Child & Adolescent Psychiatry. DOI: 10.1007/s00787-023-02311-8.
Tamm L, Epstein JN, Orban SA, Kofler MJ, Peugh JL, Becker SP. (2023). Neurocognition in Children with Cognitive Disengagement Syndrome: Accurate but Slow. Child Neuropsychology. DOI: 10.1080/09297049.2023.2185215.
Becker SP. (2020). Systematic Review: Assessment of Sluggish Cognitive Tempo Over the Past Decade. Journal of the American Academy of Child & Adolescent Psychiatry. DOI: 10.1016/j.jaac.2020.10.016.
Becker SP, Dunn NC, Fredrick JW, McBurnett K, Tamm L, Burns GL. (2024). Cognitive Disengagement Syndrome–Clinical Interview: Psychometric Support for Caregiver and Youth Versions. Psychological Assessment. DOI: 10.1037/pas0001330.
Kılınçel Ş, et al. (2026). Preliminary Efficacy of Pharmacological Treatments on Sluggish Cognitive Tempo (Cognitive Disengagement Syndrome): A Systematic Review and Meta-Analysis. Frontiers in Psychiatry. DOI: 10.3389/fpsyt.2026.1787612.
