Frequently asked questions

What does PAS-ADD stand for?

Psychiatric Assessment Schedules for Adults with Developmental Disabilities. The name is no longer strictly accurate because there is now the Child and Adolescent Psychiatric Assessment Schedule. Also, all the assessments are equally valid for the general population.

What are the distinguishing features of the PAS-ADD tools?

The PAS-ADD system has been evolving for many years, and provides a set of tools that map closely to the various roles played by health and social service staff who typically work with people who have ID and mental health problems. Over those years, several thousand people have been trained in their use, and each of these training sessions has contributed to the ongoing development of the scoring, interviewing language, and layout.

Development of the PAS-ADD assessments has adhered strictly to ICD-10 and DSM-IV decision rules. This means that they are equally valid for the general population and results can be clearly interpreted in relation to normal clinical practice. This is not the case for instruments whose development has started from the symptoms, and used psychometric principles such as factor analysis to generate item groups relating to diagnostic categories. One result of this process is that the scoring categories sometimes bear little resemblance to the diagnoses and decision rules made by clinicians.

Apart from the Checklist, the PAS-ADD assessments use tightly worded clinical glossaries to define the symptoms, and to distinguish the various levels of severity. These definitions raise reliability, and also make it easier to use by people who are less familiar with psychopathology.

Challenging (problem behaviours) are generally not covered by the PAS-ADD system.
This was a deliberate choice based on the importance of distinguishing these behaviours from psychiatric symptoms. Exceptions to this are the sections on conduct disorder and ADHD in the ChA-PAS. Of course, assessment of problem behaviours should always be undertaken by appropriate instruments if such problems exist.

The assessments use a four-point scale for rating severity. This has a number of theoretical and practical advantages. Two points are generally insufficient to encompass the range of severities that are readily distinguishable. Three points can lead to an over-emphasis on the middle point, while the status of the middle point can be uncertain. Four points enables a distinction to be made between no evidence for the symptom, and cases where the symptom certainly exists, but is below the level that is necessary for it to count towards a diagnosis.

In effect, each symptom has its own threshold in the system. This means that the upper two points can distinguish two levels of severity, both of which are significant. This corresponds to the fact that two people, both with very different symptoms severities, can both qualify for the same diagnosis. The use of the four-point scale enables close monitoring to be made of an individual during treatment. Even if the symptom remains above threshold, the change in coding will be perceived.

How can I use the PAS-ADD assessments in my service?

The PAS-ADD tools are most effective if they become part of your service policy for dealing with mental health cases. Since a main aim is the sharing of information between professionals, it makes sense for people to come together and be trained as a group. This, for example, enables the clinicians to understand what the assessments provide, and how the results can be incorporated into formal case formulation procedures. It is not suggested that every client should receive a Mini PAS-ADD. Like any procedure, the use of the assessments should be guided by clinical judgement. For instance, a call for a ChA-PAS or a PAS-ADD clinical interview to be done might be made after the first or second meeting if the clinical team has judged it appropriate.

PAS-ADD as part of a comprehensive case formulation

Understanding the significance of anyone’s mental health problems is a formidable challenge. Very often it is the person’s whole life that has brought them to the point where their problems are becoming visible, the unfolding of many factors relating to their biological status, history and current ecology. The task becomes yet more difficult if the person has reduced ability to communicate or use abstract concepts. In such cases, many symptoms, such as low self-esteem, hopelessness or delusions, become difficult to identify because they cannot reliably be inferred from external behaviours. It is like looking at the person’s problems through a distorting glass. Some symptoms, particularly problem behaviours and challenging behaviours, are highly recognisable, while many common mental health problems of low mood and anxiety can easily get lost.

We only have to think about ourselves and our life courses to realise how precious and complex our good mental health is. Good mental health requires good early attachment to a parent, successful management of drives and instincts, achievement of developmental milestones, achievement of independence and a place in society. On top of this, one’s chances of doing this are much greater if physical health and physical development are normal. In order to assess mental health, it is necessary to encompass these various perspectives, and use them to create a hypothesis explaining why the person is showing these problems at this particular time.

Many mental health services have found benefit in developing a protocol for dealing with new cases, to ensure that the relevant information is collected within each of the relevant dimensions: psychiatric, medical, ecological, behavioural, early attachment etc. Reliable, structured assessments should always be used. The PAS-ADD Assessments are designed to provide a psychiatric dimension to this broader case formulation, and training in their use includes a strong component of experience in making such formulations.

For a detailed discussion of these issues, see:
Friedlander R & Moss SC (2008) Mental health assessment of children and adolescents with learning disability. Advances in Mental Health and Learning Disabilities 2 29–36.

What disorders do the PAS-ADD assessments cover?

Each of the assessments’ descriptions list the range of disorders it covers. It has never been the aim to try and include all diagnoses, because this typically leads to an over-complexity, much of which is never used. Rather, the aim has been to provide assessments coving the more commonly occurring disorders. Other problems are then handled by using additional assessments as appropriate. Examples of the latter would be dementia and substance misuse.

Which of the PAS-ADD assessments should I use?

PAS-ADD Checklist: Screening of individuals for potential mental health problems. Doesn’t require training.

Mini PAS-ADD: Probably the most widely used of the PAS-ADD assessments. It provides a detailed picture of symptoms at two different time periods, which is designed to become part of the overall information necessary for a complete case formulation. If appropriate, community staff trained in its use can make a detailed investigation of symptoms before the case is brought to a full mental health review.

ChA-PAS: All the above information about the Mini PAS-ADD applies to the ChA-PAS. In addition, the ChA-PAS covers ADHD and conduct disorder. Some services are now using the ChA-PAS to assess young adults in transition from child to adult mental health services.

PAS-ADD clinical interview: If the person is able to give a useful clinical interview, this assessment is the one to use, because information from the person himself has unique validity. This assessment is the only one of the PAS-ADD tools that fully covers psychotic illness in detail.

The Mini PAS-ADD and ChA-PAS are very suitable for monitoring case progress because their clinical glossaries produce highly reliable measures of symptom severity, and can be completed by suitably trained non-clinicians.

Do the PAS-ADD assessments produce diagnoses?

The PAS-ADD Clinical Interview provides full criterion-by-criterion evaluation, leading to diagnoses by both ICD-10 and DSM-IV. The Mini PAS-ADD and the ChA-PAS have simplified scoring but give strong diagnostic indications for interpretation by clinicians. The sections in the ChA-PAS relating to ADHD and conduct disorder are, however, a direct embodiment of the DSM-IV diagnostic criteria relating to these particular disorders. These are therefore fully diagnostic.

Do the child and adult versions use different decision rules?

No. Both ICD-10 and DSM-IV are written to cover the entire age range.

Are there fixed age ranges for the assessments?

No. The differences between younger and older people cannot be precisely laid down on the basis of chronological age. The Mini PAS-ADD and the PAS-ADD 10 Clinical Interview were field tested on adults from 18 years upwards, but this does not mean they could not be used with younger people.

However, the glossary for the Mini PAS-ADD was written with adults in mind, which is one reason why we subsequently developed the ChA-PAS. Another reason was that child mental health services are often concerned with issues of conduct and ADHD, so this particular assessment was extended to cover these areas.

How many people with ID can respond to a PAS-ADD clinical interview.

These were the figures obtained during our study of older people with ID, and their mental health:

Rating of subject’s account of symptoms Mean IQ %
Subject responds adequately 39.2 36%
Account somewhat inadequate but interview can proceed 32.4 13%
Account seriously inadequate but interview proceeds in an attempt to rate some subjective responses 28.4 12%
Impossible to continue with interview 25.1 38%

Interestingly, it was not always possible to predict a person’s performance during the interview from their measured IQ. Some people with a severe ID could conduct quite a good clinical interview.

Is there a developmental level, below which the assessments cannot be used?

No formal lower limit is set, but of course it becomes increasingly difficult to identify symptoms as the developmental level gets lower. What tends to happen is that the more severe the ID, the more distorted our view. Any symptom that can be inferred from external behaviour, such as loss of interest, is more robust in this respect than symptoms that are more abstract. Symptoms of schizophrenia are so abstract that it is questionable whether a diagnosis can be made if the person themselves cannot give a clear verbal report.

How do DSM-IV and ICD-10 relate to the PAS-ADD system?

The DSM and ICD classification systems have moved conceptually closer together as they have developed through the various versions. In relation to the disorders covered by the PAS-ADD system, the most substantial differences are in schizophrenia, where ICD-10 has a stronger emphasis on Schneiderian first-rank symptoms. Also, symptom duration requirements are different. There are also some differences in the anxiety disorders, where DSM-IV sometimes has less emphasis on autonomic symptoms.

The Mini PAS-ADD and ChA-PAS were constructed around ICD-10 (apart from the ADHD and conduct disorder sections of the ChA-PAS). However, these assessments have a primary focus on symptom identification rather than absolute diagnosis. The threshold scores for the various diagnostic categories are based on a combination of our field trials and the criteria themselves. They are there for guidance when interpreting the results. As a result, these assessments can be readily used by staff working within either classification system.

The PAS-ADD Clinical Interview, on the other hand, does produce diagnoses (although these always remain at the discretion of the user). Every difference between DSM-IV and ICD-10, however small, has been incorporated into the scoring system.

How does the PAS-ADD Clinical Interview differ from the original PAS-ADD 10?

The PAS-ADD Clinical Interview has made the following major improvements:

Both ICD-10 and DSM-IV(TR) can be made
The scoring system has been completely changed. No computer is necessary. Scoring is fully transparent so it can be seen exactly where the person’s scores lie in relation to diagnostic requirements. Scoring now requires a minimum of flicking backwards and forwards through the pages.
The interview has been made easier to use, and now includes glossary information about each item.
The assessment now includes obsessive compulsive disorder, ADHD and an autism screen.
There is now a section to structure a full case formulation, where information from other sources can be brought together with the results of the interview. This enables case formulation to encompass not just a psychiatric framework, but also medical/physical, behavioural, ecological, family functioning and psychodynamic perspectives. The overall aim is to provide a structure within which the key elements of the case can be identified, from which the diagnostic hypotheses are then derived.

What is the psychometric status of the PAS-ADD assessments?

Field trials have been conducted on the PAS-ADD 10, Mini PAS-ADD and PAS-ADD Checklist, and these finding are reviewed under the sections dealing with each assessment. In 2010, a large-scale study of the Mini PAS-ADD has been conducted in Belgium. Results of this will be published on this website when available.

It is, however, important to be clear about the significance of these types of studies. Psychometric evaluation is usually employed to measure the effectiveness with which an instrument can measure some dimension or quality, which is otherwise difficult or time-consuming to evaluate. Intelligence, for instance, is a concept which takes a lot of expert clinical time to measure, so much effort is directed to producing assessments that are briefer to use, or require less skill. Psychometric analysis is then used to compare the performance of the experts using full assessment, versus people using a shorter instrument. This is type of evaluation is entirely appropriate to evaluating the PAS-ADD Checklist, because the aim is to do just that: to help non-qualified people identify psychiatric problems. Even in this case, however, it is important to recognise that this is not really a psychometric investigation. Psychometrics assumes there are underlying traits to be measured, that conform to certain requirements regarding their distribution. One example of the aims of this type of analysis is to show that the items in a given scale should be correlated fairly closely (because they are measuring the same thing).

The problem of applying this to assessments like the PAS-ADD is that diagnostic decision rules were not laid down by psychometricians. They have arisen over 100 years of work looking at patterns of signs and symptoms as they occur in the population. Both ICD-10 and DSM-IV embody the principle of a polydiagnostic approach ie. that two people with very different symptoms can get the same diagnosis. Also, two people with the same diagnosis can have very different aetiologies for their problem. For instance, one may have a strong biological tendency towards depression; another may have seen all her peers and siblings grow up and become independent in life while she is left behind forever; another may have had inadequate bonding with his parents, and subsequent family feuding and unrest leading to a feeling of being unloved. The problem, therefore, is that assessments of mental health are probably not best served by psychometric analysis. The appropriate items for a given disorder may not all be well correlated, simply because clinical experience has shown the need to collect information on symptoms that may not be highly correlated in the population as a whole.

When it comes to the other assessments in the PAS-ADD series, the usefulness of psychometric analysis becomes even more limited because of the absence of a ‘gold standard’. In the case of intelligence, for instance, it can be taken that results from an expert user of something like the WAIS represents the best possible measure of the trait. Away from psychometrics, the validity of a blood test for measuring kidney function can be tested against detailed examinations. In this respect, the problem of evaluating the Mini PAS-ADD or the Clinical Interview is that these instruments are themselves designed to improve the gold standard. They are not designed to estimate expert clinical opinion, but to improve the quality of that opinion.

Since the symptoms used in the PAS-ADD assessments are exactly as laid down by ICD-10 and DSM-IV, their content validity is assured. The only areas in which disagreement might occur are in relation to the minimum severity levels required by the glossary definition. Thus, clinicians may accept a less severe example of a symptom, while the PAS-ADD usually requires a moderate rating before it scores. The scoring thresholds came originally from the SCAN, the interview from which the PAS-ADD Interview was first developed. Since that time we have continued to write the glossary definitions to map closely to expert clinical opinions.

Overall, the development of the PAS-ADD assessments had been directed by an aim to maximise clinical usefulness: do they help people make better assessments in real life clinical work? So far, we are very pleased with the feedback that has been received in this respect.

Are the PAS-ADD assessments being used in research?

Yes. See PAS-ADD research.

Why do the PAS-ADD assessments give lower rates of prevalence than many published studies?

Generally speaking, studies that employ routine clinical investigation for identifying cases produce higher rates of prevalence than those that use structured assessments. This is because clinicians are trained to be sensitive to symptoms. One of the main ways of summarizing symptom information is to give diagnosis. Structured assessments, on the other hand, may be sensitive to symptoms but not give a diagnosis unless the person fully meets the necessary diagnostic criteria. This is bound to result in lower prevalence rates because there are many individuals who have some symptoms, but not enough to meet the criteria.

One anecdote that illustrates this point was a report from a group of clinicians who had been trained in the Mini PAS-ADD. They reported that it didn’t work, because only 12% of their clients were found to have a psychiatric disorder, while they believed the true rate was 40%. Our studies would suggest that the prevalence rate for people meeting World Health Organization criteria is about 11–12%, but there are of course many individuals who have some symptoms. How one deals with such cases is a practical, moral and philosophical challenge. Is it better to give a diagnosis? Quite possibly yes, if the result is access to a service stream that would otherwise be unavailable. On the other hand, it is probably better not to label people unnecessarily.

This is one reason why the PAS-ADD assessments stress the need for interpretation of the results. Even though someone is below the suggested threshold, a clinician may still decide that it is appropriate to give a diagnosis. The main aim of the tools is to provide the best possible information about symptoms. Clinicians should make the final decisions.

Do the PAS-ADD tools reduce the need for clinical training, or clinically trained staff?

Absolutely not; the emphasis of the PAS-ADD system is to help clinicians and other staff improve the accuracy and usefulness of the assessments they conduct. The input of experienced clinicians is essential to derive maximum benefit from the PAS-ADD system.

Do I need to have specific qualifications to use the assessments?

No, no specific limitations are placed on use of the PAS-ADD tools. The emphasis is on training users. Of course, a clinical background is a big advantage, particularly when it comes to interpretation and case formulation.

Do I need training?

Yes. All the PAS-ADD assessments, with the exception of the Checklist, are designed for trained raters. Here you can download documents relating to training in the Mini PAS-ADD and the ChA-PAS

For advanced interviewing training using the PAS-ADD Clinical Interview, please email us to discuss your requirements.

Do I need training if I am a psychiatrist or psychologist?

Yes. The core skills of using the clinical glossary and using the semi-structured interview are specific to these assessments, and need guided practice. Over many years of training people to use the PAS-ADD assessments, it has been clear that the best training sessions are those that include all relevant staff. They not only learn from each others perspectives, but also get the opportunity to share ideas about mental health and mental illness.

How can I access training?

At the moment the main person conducting training sessions is the author. However, we are currently looking at developing other ways to provide training.

If you are an individual, the Estia Centre at King’s College London run regular courses. Please contact the Centre for the next course.

If you are a group of people requiring training, Dr Moss can arrange a visit, both in the UK and internationally. European visits can be easily arranged. Dr Moss makes regular visits to Australia, and it is planned for him to offer regular training visits to North America. Please contact Dr Moss if you are interested in arranging training.

Who should I contact for questions about PAS-ADD, bulk orders, or translation rights?

Please direct all questions about PAS-ADD to and a member of the team will be pleased to assist.