ADHD or Autism? Understanding the Difference When They Seem Alike

For many adults seeking a diagnosis, one question comes up time and again: Am I autistic or do I have ADHD (Attention Deficit Hyperactivity Disorder)? While the two profiles share certain characteristics, they stem from very different cognitive and neurological mechanisms.

Understanding the difference is key to avoiding diagnostic confusion and tailoring the right therapeutic support to each person’s needs.

Shared Symptoms, Different Causes

Both ADHD and autism can involve:

• difficulties concentrating or maintaining attention;

• impulsivity (verbal, emotional, or behavioural);

• problems with organisation;

• intolerance to waiting or boredom;

• a persistent sense of being socially “out of step”.

  
  

➡️ This overlap explains why co-occurrence is common: it’s estimated that 30 to 80% of autistic individuals also present signs of ADHD (Leitner, 2014).

But Different Underlying Mechanisms

Despite similar traits, the root causes are not the same.

• ADHD is linked to dysfunctions in attentional and executive systems, especially dopamine and noradrenaline regulation (Barkley, 1997).

• Autism, on the other hand, stems from a distinct cognitive organisation: detail-focused perception, rigidity in routines, differences in social cognition, and sensory overload.

🧠 For example:

• A child who interrupts class may, if they have ADHD, simply be impulsive and distracted.

• If they’re autistic, the interruption may stem from a need to correct a factual error (literal thinking, need for precision), or from sensory discomfort.

  
  

Relationship with Time and Motivation

• In ADHD, time is often abstract or blurred: procrastination, hyperfocus on enjoyable tasks, difficulty with planning (Barkley, 2001).

• In autism, the relationship to time tends to be rigid: fixed routines, intolerance to change, anxiety in the face of unpredictability.

➡️ The driver for ADHD is stimulation; for autism, it’s predictability.

Interests and Stimuli

• ADHD typically involves a constant search for novelty and varied stimulation.

• Autism is characterised more by deep, focused interests, which may be intense but also soothing.

💡 A person with ADHD may jump from one hobby to another. An autistic individual may delve into a single subject for years with consistent intensity.

What About Women?

Women are particularly vulnerable to misdiagnosis. ADHD in women is often of the inattentive type, less overt than in boys. Autism, meanwhile, may be masked by significant efforts to conform socially (Lai et al., 2015).

➡️ As a result, many women are diagnosed with ADHD… when their overall functioning is more closely aligned with autism.

Key Differences to Look Out For

Here’s a quick comparison table:

Functioning area	ADHD	Autism
Attention	Fluctuating, easily distracted	Focused or absent, depending on interest
Organisation	Disorganised, impulsive	Structured, rigid or routine-based
Social interaction	Impulsive, occasionally excessive	Selective, distant or rule-based
Sensory profile	Less prominent (unless co-occurring autism)	Often highly sensitive
Interests	Varied, novelty-seeking	Specific, stable, comforting

In Short

• These two profiles may overlap, but their foundations differ.

• ADHD is driven by a need for movement, variety, and stimulation.

• Autism reflects a unique way of interacting with the world — centred on consistency, coherence, and often, sensory regulation.

• If you relate to one or both, it’s essential to consult a professional who specialises in neurodevelopmental conditions.

  
  

📚 Further Reading

• Barkley, R. A. (1997). Behavioural inhibition, sustained attention, and executive functions: Constructing a unifying theory of ADHD. Psychological Bulletin.

• Leitner, Y. (2014). The co-occurrence of autism and attention deficit hyperactivity disorder in children – what do we know? Frontiers in Human Neuroscience.

• American Psychiatric Association. (2013). DSM-5 Diagnostic and Statistical Manual of Mental Disorders.

• Lai, M.-C., Lombardo, M. V., Auyeung, B., Chakrabarti, B., & Baron-Cohen, S. (2015). Sex/gender differences and autism: Setting the scene for future research. Journal of the American Academy of Child and Adolescent Psychiatry.