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Agreement Between Self- and Parent-Reports of Prodromal Psychotic Symptomatology
Georgia A. Scheele, Rachel L. Loewy, M.A., and Tyrone D. Cannon, Ph.D. University of California, Los Angeles
This research was supported by the Music Festival for Mental Health and a gift from Garen and Shari Staglin. Abstract The schizophrenia prodrome has gained considerable research attention in recent years. Early identification of individuals at risk for psychotic disorders may improve outcomes for those individuals, as well as identify participants for research that aims to develop effective intervention strategies for this population. Effective screening methods from multiple parents facilitate identification and aid in accurately ascertaining the symptom picture for this population. In this study, the Prodromal States Questionnaire (PSQ) was completed by 27 participant-parent pairs who were referred for intake assessments to the Center for the Assessment and Prevention of Prodromal States at UCLA. The PSQ consists of a 92-item self-report measure of prodromal symptomatology, along with a parallel version for parents or other informants. Items are divided into major scales of positive, negative, disorganized, and general symptoms. Inter-rater agreement was analyzed using Cohen's Kappa statistic (k). Twenty-one subscale items reached the 'moderate' agreement criterion of .41 k or above. None of the scale averages showed good agreement. The majority of individual subscale items that showed good agreement were positive symptoms. Although these data preliminarily suggest higher agreement on positive symptom presence, further research and comparison with clinician ratings are needed.
Agreement Between Self- and Parent-Reports of Prodromal Psychotic Symptomatology In
recent years, the prodrome has become a focal point in schizophrenia
research (Cornblatt, Lencz, & Obuchowski, 2001; Rosen, Woods, Miller,
& McGlashan, 2002). The 'prodrome'
is described as "the early symptoms and signs of an illness that
precede the characteristic manifestations of the acute, fully developed
illness" (Yung & McGorry, 1996). The prodromal phase in
schizophrenia is an important area of study because early intervention
with individuals at risk of developing the disease may help lead to better
outcomes (McGlashan, 1996; McGorry et al., 1996). A prolonged 'duration of
untreated psychosis' (DUP) for participants who have already converted to
schizophrenia has been associated with increased severity, persistence,
and global damage done by the disorder (McGlashan, Miller, & Woods,
2001). It is hoped that prospective research into the etiology and course
of this illness may help researchers develop an intervention protocol for
those at risk (McGorry, 1999). Yung
and colleagues (1996) have determined a set of research symptom criteria
that define three types of prodromal syndromes, based on retrospective
reports of schizophrenia patients and their relatives. These criteria have
been modified slightly by McGlashan, Miller, and Woods (2001) and can be
reliably assessed by using the Structured Interview for Prodromal
Syndromes (SIPS). The SIPS
identifies a ‘vulnerability group,’ which includes individuals who
have had a precipitous decline in functioning in the last year along with
either a first-degree relative with a psychotic disorder or a diagnosis of
Schizotypal Personality Disorder (American Psychiatric Association, 1994).
The ‘attenuated symptom’ group includes individuals with sub-threshold
psychotic symptoms, such as hearing whispers of voices or excessive
suspiciousness. The ‘brief
limited psychosis’ group includes individuals who have recently
experienced fully psychotic symptoms for very brief periods of time.
Individuals diagnosed as prodromal according to the SIPS have a 54%
chance of developing a psychotic disorder within one year
(Miller et al., 2002). The SIPS requires ratings in four symptom
categories: ‘positive’ symptoms (such as delusions, suspiciousness,
and hallucinations), ‘negative’ symptoms (such as withdrawal and
decreased experience of emotion), ‘disorganized’ symptoms (such as odd
behavior or bizarre thinking), and ‘general’ symptoms (such as sleep
and motor disturbance). Most
previous studies of the prodrome have involved retrospective research with
individuals who have already converted to schizophrenia or their
first-degree relatives. However,
neither technique allows for the study of prodromal symptoms as they
unfold. Prospective research is critical in order to perform repeated
measures over time through the onset of the disorder. This increases
accurate symptom measurement and allows for the unmasking of schizophrenia
predictors that cannot be studied by other means. The eventual goal of
such research is to prospectively identify individuals at risk early
enough so that intervention can take place. Data have preliminarily
suggested that early intervention may reduce the likelihood that prodromal
individuals develop psychosis (Falloon, 1992).
This
sort of research requires that prodromal individuals be accurately and
effectively identified in the population. Brief screening measures can
help to identify those who might benefit from a full-length interview and
who might be at risk for development of psychosis. Once such individuals
have been identified, their symptom experience can be monitored. Although
first hand accounts from prodromal individuals are the primary source of
information about their symptoms, reports from family members and other
parents can also help to better illustrate the symptom picture and aid in
early detection. A certain amount of disagreement is expected, and the
parent contribution can provide information that the prodromal individual
does not or cannot provide. For example, a parent might accurately report
about certain symptom areas where the participant lacks insight or
awareness, or is guarded about describing his or her experience.
Eventually, a comparison of both reports to clinician ratings can be made
so that it can be determined who is more aligned, child or parent, with
the clinician ratings. In
order for such research to become a possibility, it is necessary to
accurately and effectively identify prodromal individuals, their symptoms,
and how accurately they report these symptoms. Examining the degree of
agreement between self- and parent-reports can help to determine which
sources of information should be used in screening and diagnosing
prodromal syndromes. This is
the aim of the study at hand. The
present research utilizes a prospective research methodology. Data were
collected from multiple informants (including parents, other relatives,
and significant others whom from here after will be referred to as
parents). Participant and parent reports of prodromal symptomatology were
measured using the Prodromal States Questionnaire (PSQ; Loewy, Cannon,
& Raine, 2002). Analyses examined agreement between reporters (self
and parent). Although the study at hand was conducted as part of a larger
research protocol investigating the prodromal phase by tracking prodromal
participants over time, the current analyses are limited to data collected
at the first time point. Once follow-up data have been collected, further
analyses can be made. It is an eventual goal of this research to measure
comparison with clinician ratings and the predictive validity of the PSQ
by tracing who develops the illness. The present study, however, will
focus solely on participant/parent agreement on the PSQ at baseline. Method Participants
The sample included 27 participant-parent pairs. Participants were
18 females and 9 males. Parents were 24 females and 3 males (23 mothers, 3
fathers, and 1 female significant other of a participant). Participants
were referred to the Center for the Assessment and Prevention of Prodromal
States (CAPPS) at UCLA. CAPPS is a program that seeks to identify and
treat individuals at risk for development of schizophrenia and other
psychotic disorders. Referrals came from clinicians in the community and local
schools. All participants were financially compensated for their
participation. Based on answers to the Structured Interview for Prodromal
States (SIPS), participants who met criteria for a prodromal syndrome were
included in the research study (N = 12) while individuals who met criteria
for psychosis, substance dependence, declined to participate, or did not
otherwise meet prodromal criteria were excluded from the larger study (N =
15). This analysis includes both included and excluded participants.
Although in some cases more than one parent completed a PSQ, preference
was given to questionnaires completed by mothers, fathers, then
significant others, in that order. All participants gave their informed
consent. Measures The
SIPS was used to assess the presence of prodromal symptom criteria. The
SIPS is an interview developed by Miller and colleagues (2002) to diagnose
prodromal individuals. Items on the SIPS are divided into major scales
including positive symptoms, negative symptoms, disorganized symptoms, and
general symptoms. All
participants completed the Prodromal States Questionnaire (PSQ), which is
a 92-item self-report measure with true/false answers. The questionnaire
takes about 15 minutes to complete. Answers are divided into four major
scales that measure positive, negative, disorganized, and general symptoms
(identical to the SIPS). Questions
include items adapted from the Schizotypal Personality Questionnaire (SPQ)
(Raine, 1991) as well as SIPS probe questions. Several original items were
also added to the questionnaire. Preliminary
analyses indicate that the self-report version of the PSQ has good
psychometric properties and shows good concurrent validity with SIPS
diagnoses (Loewy, et al., 2002). Procedure All
participants and their parents completed the PSQ at the intake assessment
at CAPPS. Every effort was
made to ensure that parents and children completed the questionnaires
separately. Interviewers
administered the SIPS to determine study eligibility. All participants
answered the positive symptom scale questions on the SIPS, but some
excluded individuals did not complete the full interview if it was clear
that they did not meet criteria for a prodromal syndrome. Results Cohen’s Kappa statistic (k), which assesses
inter-rater agreement on categorical variables, was used to analyze
agreement between the participant/parent pairs for each item of the PSQ.
Agreement level was interpreted using the guide provided by Landis &
Koch (1977). Table 1 provides a list of the agreement criteria suggestions
made by Landis & Koch. Out of 92 items on the PSQ, 21 items reached
the “moderate” (k ³
.41) agreement criterion. The remaining 71 items showed agreement in the
range of k = -.40 to .40. A
list of individual item kappa scores for items showing moderate agreement
or above is provided in Table 2. Figure 1 depicts the percentage of items
within each subscale that reached the moderate or above criterion level.
Within-subscale kappa averages ranged from .14 to .44. Only one subscale
average, “olfactory hallucinations”, showed moderate agreement (k =
.44). None of the major scale averages reached the moderate agreement
criterion. Average kappa scores for both major scales and subscales are
listed in Table 3. Discussion The
participants and parents demonstrated agreement on a number of items. They
also disagreed on numerous items, suggesting that parents have some
additional information to contribute to a child’s report. These data
show moderate agreement between parents and their children on 23% of the
PSQ items. A higher
percentage of positive symptom items reached the moderate agreement
criterion (33%) than the other scales. The CAPPS clinic sample is a
referred, treatment-seeking group. This may play a role in the high
agreement for positive symptoms, as these tend to be presenting symptoms
that are the reason for seeking treatment at CAPPS.
It is possible that a general clinic or school sample might show a
different disbursement amongst the symptom categories. Overall,
there is a high level of disagreement between the participant and parent
reports. At this point, the source of parent/child disagreement is not
known. Possible
explanations for disagreement include participant non-reporting or
non-awareness of a present symptom, and parent non-reporting or
non-awareness of a particular symptom. The disagreement between parent and child reports shown in this
study may indicate that both perspectives are useful in screening for
prodromal symptoms of psychosis. Further
research in these areas is necessary in order to determine the utility and
scope of parent reports. Eventually, a
comparison to SIPS clinician ratings would show whether child or parent
ratings are more in line with ratings made by clinicians. This
sort of data would aid researchers to understand in what instances it is
most important to get a parent report. Predictive validity of the PSQ items will also be
examined when the participants diagnosed as prodromal are assessed over
time, through the risk period for conversion to psychosis. Most important
to this research area is whether a parent’s report contributes any
predictive power to the participant’s report. It will also be valuable
to monitor what particular symptoms are most predictive of conversion. The
gathering of more PSQ data from clinic and general population samples,
comparison to parent reports, and tracking over time should help provide
answers for these questions. Although these data suggest that parents can provide a great deal of symptom information in addition to their child’s self-report, further investigation will help to clarify the specific reasons for discrepant agreement. Once a better understanding of this relationship has been attained, and the degree of agreement between parents and clinician symptom ratings have been established, the utility of the parent-report version of the PSQ as a screening device can be assessed. If found effective, the informant PSQ can be utilized in psychiatric facilities and elsewhere to help identify who may be at risk for the eventual development of psychosis and provide an opportunity for intervention at this early stage. References Achenbach,
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