The SANS (Scale for the Assessment of Negative Symptoms)

The Scale for the Assessment of Negative Symptoms (SANS) was developed by Nancy Andreasen in the early 1980s as a complement to the SAPS. Its publication marked a turning point in schizophrenia research because it forced the field to operationalise something that had been chronically under-measured: the negative symptoms — the absences, the flatness, the loss of motivation and pleasure. Until the SANS, scales like the BPRS captured negative symptoms only superficially, in one or two items.

Structure

The SANS has 25 items grouped into five domains:

• Affective flattening or blunting (8 items) — unchanging facial expression, decreased spontaneous movements, paucity of expressive gestures, poor eye contact, affective non-responsivity, lack of vocal inflections, inappropriate affect, and a global rating.
• Alogia (5 items) — poverty of speech, poverty of content of speech, blocking, increased latency of response, and a global rating. See our alogia article.
• Avolition/apathy (4 items) — grooming and hygiene, impersistence at work or school, physical anergia, and a global rating. See our avolition article.
• Anhedonia/asociality (5 items) — recreational interests, sexual interest, ability to feel intimacy and closeness, relationships with friends and peers, and a global rating. See our anhedonia article.
• Attention (3 items) — social inattentiveness, inattentiveness during testing, and a global rating.

Each item is rated 0 (none) to 5 (severe). Composite scores can be calculated as the sum of all 25 items, or the sum of the five global ratings (range 0–25), depending on study convention.

Why measuring negative symptoms is hard

Hallucinations and delusions are events you can ask about. Negative symptoms are absences, and absences are hard to interview. A patient who has not enjoyed anything in three weeks may not bring it up unprompted. A clinician sitting across from a person with flat affect may misread the flatness as boredom, depression, or even hostility. The SANS was a deliberate attempt to anchor these hard-to-measure phenomena in observable behavioural cues.

The "primary versus secondary" problem

The most criticised feature of the SANS is also the most important problem in negative symptom research generally: it does not distinguish between primary negative symptoms (the disease itself) and secondary negative symptoms (caused by depression, antipsychotic medication, social isolation, environment, or substance use). A patient on a high dose of haloperidol may look identical on the SANS to one with severe primary negative symptoms — but the right treatment is completely different.

This limitation has driven the development of newer scales:

• Brief Negative Symptom Scale (BNSS) — 13 items emphasising five domains (anhedonia, asociality, avolition, blunted affect, alogia)
• Clinical Assessment Interview for Negative Symptoms (CAINS) — separates motivation/pleasure (experience) from expression

Both newer scales drop the SANS attention domain (now usually measured separately as a cognitive symptom), which improves construct purity.

How it is administered

The SANS is rated on the basis of a clinical interview combined with behavioural observation, ideally over more than one encounter. Items like grooming and hygiene benefit from collateral information from staff, family, or housing providers. The interview takes 30 to 40 minutes for a trained rater. As with the SAPS, training and inter-rater reliability checks are essential, particularly for the more subjective affective flattening items.

Time frame

Most items are rated based on behaviour over the past month. Some items (poverty of content, latency, blocking) can be rated based on the interview itself.

Strengths

• The most detailed coverage of negative symptoms of any first-generation scale
• Public domain and freely available
• Decades of accumulated data, including pairings with the SAPS in many cohort studies
• Anchor descriptions are concrete and observable

Limitations

• Cannot distinguish primary from secondary negative symptoms — a major weakness
• Includes attention as a "negative symptom," which is now considered a separate cognitive domain
• Some items (inappropriate affect under flattening) overlap with positive symptoms
• Sensitive to medication-induced parkinsonism, which can inflate flattening scores

What this looks like in clinical research

Drug development for negative symptoms is one of the hardest open problems in psychiatry. As reviewed in coverage from the NIMH, no medication has been approved with a primary indication for negative symptoms. Most antipsychotics show only modest effects on the SANS. The newer cariprazine has shown some advantage in head-to-head trials, but the field remains active. The choice of scale matters: studies that use the SANS sometimes show different effect sizes from those using the BNSS or CAINS, which affects how findings should be compared.

What this means for patients and families

If a clinician describes your symptoms with words like "blunted affect" or "anhedonia," they are using the language of the SANS family of scales. Knowing that vocabulary is helpful for decoding clinic notes and trial descriptions. It is also worth understanding that a "high SANS score" does not mean someone is more disabled or less capable — it means a particular set of behavioural patterns is observed at one moment in time. People move on the SANS, especially with engagement, structure, and the right combination of medication and psychosocial support.

This article is for educational purposes only and is not medical advice, diagnosis, or treatment. Always consult a qualified mental health professional. If you or someone you know is in crisis, call or text 988 in the US, or your local emergency number.