A briefing on aphantasia and SDAM.

The two terms in one sentence each

• Aphantasia — the inability, or severely reduced ability, to form voluntary mental imagery. Most often visual, but can be multi-sensory. Coined by Zeman and colleagues at Exeter, 2015.
• SDAM — Severely Deficient Autobiographical Memory. A lifelong pattern of preserved semantic knowledge about one’s life with markedly reduced capacity to mentally re-experience past events. Described by Palombo and colleagues at the Rotman Research Institute, 2015.

The two frequently co-occur but are dissociable. Neither is in the DSM-5 or the ICD-11. Neither has an established treatment. Neither is a disorder in the clinical sense.

Prevalence

Estimates for congenital aphantasia range from approximately 1% to 5% of the population, depending on VVIQ cut-off. Hyperphantasia (the high end of the same spectrum) is of similar order. SDAM is less well-characterised in population terms; the working estimate is lower but non-trivial, with a meaningful overlap with aphantasia. In a typical UK general-practice list size of ~1,800, a GP can expect several dozen patients with some degree of imagery or autobiographical-memory atypicality.

What patients are usually asking for

Almost always validation, not treatment. A patient who raises aphantasia or SDAM in a UK GP consultation has usually:

1. Self-identified after reading, often in the past few weeks.
2. Taken a VVIQ or SAM questionnaire and scored at the relevant extreme.
3. Wanted to mention it for the record, or to rule out that it is relevant to something else they are presenting with.

They are not usually asking for a referral, a scan, or a treatment plan. They are often asking to not be dismissed, and to have the term recorded on their notes in case it is useful later.

A short script that tends to land well

For the clinician with a few minutes to respond:

Clinicians who have not come across the term before can equally say so — there is no professional cost. A useful fallback is: “I will make a note and look this up; thank you for telling me”.

What not to do

• Do not dismiss. The research base is genuinely real (Zeman’s 2025 decade review is a good entry point). Patients who are dismissed typically leave and do not return — a small harm that the NHS absorbs silently.
• Do not pathologise. Aphantasia and SDAM are not indicators of dissociation, depression, autism, ADHD, or dementia, though any of these may co-occur. The distinguishing feature is that aphantasia and SDAM are lifelong, stable patterns — not changes from a previous baseline.
• Do not offer visualisation training. No training has been shown to reliably produce imagery in people who lack it. Exercises may help mood and focus via other mechanisms but should not be offered as a “treatment” for aphantasia itself.
• Do not screen with homemade tests. The VVIQ and the SAM are validated and widely used; re-implementations are not. If the patient has not taken the real thing, pointing them at the validated instrument (see the resources page) is sufficient.

When to worry (and what to worry about)

Lifelong aphantasia and SDAM are not, themselves, cause for concern. The situations that are worth attention:

• Acute-onset aphantasia. A patient reporting sudden loss of previously intact mental imagery warrants the usual workup for an acquired neurological event — this is a distinct clinical picture from the lifelong form.
• Recent memory change framed as SDAM. SDAM is a lifelong baseline; a recent shift toward reduced autobiographical recall is not SDAM and warrants standard cognitive assessment.
• Emotional load. The recognition of aphantasia or SDAM can precipitate low mood, grief, and in some cases rumination on missing childhood memories. This is the clinical thing to watch for and, where relevant, support. It is not caused by aphantasia or SDAM; it is caused by the realisation.

UK research groups you can point patients toward

• The University of Exeter (Adam Zeman’s group) — the UK academic home of aphantasia research, including the Eye’s Mind project. Actively recruiting participants.
• The University of Glasgow (Fiona Macpherson’s consciousness and imagination programme).
• The Rotman Research Institute, Toronto — the main SDAM research home; accepts international participants.

Current study links live on the resources page.

A suggested entry on the patient record

Further reading

• Zeman, A. (2025). A decade of aphantasia research — and still going! Neuropsychologia. A readable review for clinicians.
• Palombo, D. J., Alain, C., Söderlund, H., Khuu, W., & Levine, B. (2015). Severely Deficient Autobiographical Memory (SDAM) in Healthy Adults. Neuropsychologia.
• The cornerstone guide on this site — longer form, fully cited, written to be readable alongside a patient.

If you want to contribute

Clinicians and educators with an interest in improving UK awareness of these conditions are warmly invited to contact us via the about page. We are particularly interested in CPD collaborations with UK academic groups from late 2026 onwards.