ICOSR 2007—NAPLS Targets the Schizophrenia Prodrome
Editor's Note: A symposium on Friday, 30 March 2007, at the International Congress on Schizophrenia Research in Colorado Springs, detailed progress in prodromal research. Wendy Hasenkamp, from the Atlanta VA/Emory School of Medicine, reports here on "The North American Prodrome Longitudinal Study: a multi-site approach to prodromal schizophrenia research."
22 April 2007. Studies show that early treatment of psychosis is related to improved clinical outcome in schizophrenia (McGlashan, 1988; 1998; also see SRF related news story). The critical time period before the onset of psychosis during which functional impairments emerge and attenuated symptoms may be identified is known as the schizophrenia prodrome. The prodrome is characterized by symptoms such as cognitive impairments, marked social and/or behavioral decline, and changes in affect (emergence of anxiety and depression). In hopes of improving the possibility of early detection and intervention, as well as furthering our understanding of the developmental process underlying psychotic disorders, research has recently intensified in the once-controversial area of the schizophrenia prodrome (an SRF related news story summarizes some recent developments in this field). In 2004, principal investigators for eight research projects in the U.S. and Canada agreed to combine data on psychosis risk factors and clinical outcomes for nearly 900 subjects enrolled in prodromal schizophrenia research programs. This consortium, known as the North American Prodrome Longitudinal Study (NAPLS) is under the direction of Robert Heinssen at the NIMH (Addington et al., 2007). The 10 participating investigators are Jean Addington (University of Toronto), Kristin Cadenhead and Ming Tsuang (UCSD), Tyrone Cannon (UCLA), Barbara Cornblatt (Zucker Hillside Hospital), Thomas McGlashan and Scott Woods (Yale University), Diana Perkins (UNC Chapel Hill), Larry Seidman (Harvard University), and Elaine Walker (Emory University). The NAPLS symposium at ICOSR marked the second time that the consortium has presented its early findings, the first being in Birmingham, England, last October at the 5th International Conference on Early Psychosis.
Jean Addington served as chair, and began the symposium with an overview of the consortium’s methods and operational definitions. To ensure comparability of data across the eight sites, all NAPLS researchers use the same diagnostic criteria to identify individuals with prodromal symptoms. The Structured Interview for Prodromal Syndromes (SIPS; Miller et al., 2003), created by Thomas McGlashan, was employed to rate each subject on the degree of severity of five classes of symptoms: unusual thought content/delusional ideas, suspiciousness, grandiosity, perceptual abnormalities, and conceptual disorganization. Based on SIPS scores, the consortium has identified three prodromal syndromes: attenuated psychotic symptoms (APS), genetic risk plus deterioration (GRD), and brief intermittent psychotic symptoms (BIPS). Addington then described how the current NAPLS subjects were divided into six groups: individuals believed to be at heightened risk for psychosis (HRP); those at genetic high risk but without prodromal symptoms; those who meet criteria for schizotypal personality disorder but do not display prodromal symptoms; those who have already developed psychotic symptoms; and two comparison groups, those who failed to meet criteria for being at elevated risk (helpseekers), and non-psychiatric controls. Having explained the basic approach of the consortium, Addington turned the floor over to three NAPLS members who detailed more specific questions being asked about this interesting prodromal subject population.
Sifting through these many abbreviations adopted by NAPLS to describe syndromes and subgroups, Tyrone Cannon discussed the rate of conversion to psychosis within the sample. Conversion was defined as one or more positive symptoms reaching the psychotic level of conviction, frequency, and duration (>1 hour/day for 4 or more days within the past month) and impact (disorganizing or dangerous). Among the HRP subjects, risk for conversion was 17 percent per year, with an ultimate conversion rate of 35 percent after 30 months of follow-up. Delving deeper, Cannon explained his efforts to improve our ability to predict the likelihood of conversion for a given individual based on initial risk factors. His group identified five variables (a mixture of SIPS scores and clinical, neurocognitive, and historical variables assessed at baseline) as being the most important for successful for prediction: genetic risk with decreased functioning, unusual thought content, suspicion/paranoia, level of social functioning, and drug use of any kind. Using a single-variable model, the positive prediction power reached 50 percent; Cannon suggested that about 80 percent would be needed to justify pre-emptive intervention programs. However, when more variables were added to the model, positive predictive power improved. Models incorporating two out of five symptoms reached up to 69 percent, while three out of five symptoms yielded up to 74 percent. However, gains in predictive power were achieved with corresponding losses in sensitivity of the models. While still a work in progress, these findings suggest that NAPLS efforts are resulting in improved risk ascertainment algorithms, which may help identify individuals for early intervention.
Barbara Cornblatt continued the discussion by describing her work on relating the duration of prodromal symptoms to clinical outcome. To determine the outcome associated with earlier-appearing symptoms, she compared two similar subject groups. The first comprised 357 individuals who, based on SIPS criteria, displayed moderate to severe attenuated positive symptoms for 12 months or less (APS); the second group was 100 subjects who met the same SIPS criteria, but had a longer duration of symptoms (long duration prodromals, LDP). She found that after 30 months, the APS group had a conversion rate of 38 percent compared to only 14 percent in the LDP group. However, she noted the caveat that LDP subjects were younger and more functionally impaired than APS subjects, but had a lower degree of severity of positive symptoms. This suggests that the LDP group may be at an earlier phase of illness and conversion rates may increase with continued follow-up. Cornblatt concluded that while this study gave strong support for the predictive validity of the APS syndrome as defined by the SIPS, the results also suggest that LDP may be a risk group of its own, and perhaps a longer risk window should be incorporated into future prodromal studies.
The last NAPLS member to speak at the symposium was Diana Perkins, who focused on the development of various functional impairments throughout the prodrome. In order to compare data on functional outcomes across sites, Cannon and Cornblatt have developed two 10-point scales rating social (Global Social Functioning Scale, GSFS) and vocational (Instrumental Role Functional Scale, IRFS) functioning (Cornblatt et al., 2007). Perkins examined the 357 subjects who met SIPS criteria for APS, as well as the 11 subjects who were classified as having BIPS syndrome. Using scores from the new social and vocational functioning sales, she compared these “at-risk” subjects to 196 healthy comparison subjects. She found, as expected, that the at-risk group had lower scores on both the social and vocational functioning scales, as well as lower Global Assessment of Function (GAF) scores, than the healthy controls. Perhaps most importantly, however, the at-risk subjects had experienced a significantly greater decline in function (as measured by the change in scores on the GSFS, IRFS and GAF) than controls in the year prior to analysis. Thus, Perkins suggested that early identification and intervention may be helped by targeting the initial declines in social and vocational functioning that are seen in these at-risk states.
The NAPLS consortium has recently published its rationale, design, and some preliminary findings in Schizophrenia Bulletin (Addington et al., 2007). NAPLS is one of two large collaborative studies of populations at clinical or genetic risk for psychosis; the European Prediction of Psychosis Study (EPOS) is made up of six sites and undertakes similar research in Europe (Klosterkotter et al., 2005). It is thanks to groups like these that we may soon have improved ability to target psychosis and hopefully provide much needed intervention at the early stages of psychiatric disease.— Wendy Hasenkamp.
Comments on News and Primary Papers
Comment by: Tara Niendam
Submitted 11 May 2007
Posted 11 May 2007
I just wanted to clarify a mistake in the article above. The new social and role functioning measures discussed by Barbara Cornblatt were incorrectly identified. The correct titles are Global Functioning Scale: Social (Auther et al., 2006) and Global Functioning Scale: Role (Niendam et al., 2006). Data on these new measures were recently published as part of a collaboration between LIJ and UCLA (Cornblatt et al., 2007). The references for these measures are listed below. Researchers interested in using these measures can contact either author (A. Auther or T. Niendam) for copies of the measures.
Auther, A.M., Smith, C.W. & Cornblatt, B.A. (2006). Global Functioning: Social Scale (GF: Social). Glen Oaks, NY: Zucker Hillside Hospital.
Niendam, T.A., Bearden, C.E., Johnson, J.K. & Cannon, T.D. (2006). Global Functioning: Role Scale (GF: Role). Los Angeles: University of California, Los Angeles.
View all comments by Tara NiendamComment by: Patrick McGorry, Alison Yung (Disclosure)
Submitted 17 May 2007
Posted 18 May 2007
The key issue of the confounding of the transition process and the related predictive analyses by uncontrolled treatment, especially with antipsychotic medications, has not been highlighted in the report. It would be illuminating to ask the collaborators to comment on this issue in the Forum. The randomized controlled trial conducted by Dr. McGlashan and colleagues (many of whom are now NAPLS investigators) was a stronger design since it contained a placebo arm which allows purer study of the prediction issue ( McGlashan et al., 2006). This should be supported in the future by NIMH and other funders in our opinion.
View all comments by Patrick McGorry
View all comments by Alison YungComment by: Tyrone Cannon
Submitted 5 September 2008
Posted 6 September 2008
The case for testing antipsychotic drugs as prophylactic measures rests entirely on their empirically proven efficacy in decreasing the severity of positive psychotic symptoms among patients with established illness. Initial applications of these agents in studies of prodromal patients have produced discouraging results on the primary question of preventive effects. Among patients with established illness whose positive symptoms respond to antipsychotics, such treatment must be continuous in order to maintain treatment gains; it is therefore not surprising that trials of antipsychotics in prodromal patients would show effects of drug on positive symptom reduction only during the active treatment phase. With no demonstrable prophylactic effects, and with little or no effect on motivational symptoms or functional disability, antipsychotic drug treatment in the prodromal phase is clearly not the “silver bullet” of psychosis prevention.
Some have suggested that randomized controlled studies of antipsychotics provide the most coherent platform from which to monitor natural progression of the prodromal phase, since there is no confounding of progressive processes and treatment effects among individuals assigned to placebo. However, the ability to identify predictors and mechanisms of psychosis depends critically on the enrollment of large samples of prodromal subjects who are representative of the at-risk population. In the antipsychotic drug trials with prodromal patients, only a small fraction (on the order of 25 percent to 40 percent) of the potential subjects who screened as eligible for inclusion in the studies consented for participation and enrolled in the trials. Further, a relatively large fraction (on the order of 30 to 50 percent) of the initially enrolled subjects withdrew from these studies during the active treatment phase or follow-up period. Low rates of consent for participation combined with high attrition rates (likely due at least partially to side effects of drug treatments) have been reported in all prodromal randomized clinical trials and can thus be expected to severely constrain the generalizability of findings related to prediction and mechanisms of onset in such studies.
Therefore, ideally the next wave of studies into the natural progression of neurobiological factors in prodromal patients will employ a treatment algorithm by which antipsychotics are not prescribed until a patient displays positive symptoms at a fully psychotic level of intensity. This design will result in standardization of treatment across the participating sites and avoid confounding antipsychotic drug treatment with measurements of the biological processes hypothesized to underlie progression to psychosis.
View all comments by Tyrone Cannon
Comments on Related News
Related News: Schizophrenia and Neurodegeneration—Case Bolstered by MRI, ElectrophysiologyComment by: Dan Javitt, SRF Advisor
Submitted 29 May 2007
Posted 29 May 2007
Salisbury et al., in the May 2007 issue of Archives of General Psychiatry, demonstrate associated progressive reductions in mismatch negativity (MMN) amplitude and Heschl’s gyrus reduction in schizophrenia. These findings provide strong support for involvement of auditory cortex in the pathogenesis of schizophrenia, and demonstrate that pathological changes in the illness are not confined to specific brain regions, such as prefrontal cortex, that receive the preponderance of attention.
Further, the manuscript helps resolve an important current controversy in the MMN literature. Deficits in MMN generation have been among the most consistent findings in chronic schizophrenia, with a recent meta-analysis showing large (~1 sd unit) effect size MMN reductions across studies (Umbricht et al., 2005). As noted by Salisbury et al., however, deficits have not been observed in first-episode patients (Salisbury et al., 2002; Umbricht et al., 2006). An unknown issue was whether the discrepancy between first-episode and chronic patients was due to within-subject change (the “degeneration” hypothesis), or whether those patients with small MMN at entry tended to be retained disproportionately in chronic samples because of the relationship between MMN generation and global outcome (e.g., Light and Braff, 2005) (the “distillation” hypothesis).
The present study suggests that at least some patients show reductions of both MMN amplitude and left HG volumes over time, lending at least partial support for the degeneration hypothesis. This finding is important in that it shows that the pathological process contributing to cognitive impairment in schizophrenia continues beyond first episode, and may be a target for pro-cognitive interventions. It should be noted that the degeneration continued despite treatment with atypical, as well as typical, antipsychotic medication.
As noted by Salisbury et al., the change in MR volume in schizophrenia is best conceived as atrophy of neurons, rather than degeneration. On a histological level, the volume reductions noted on MR correspond with reduced pyramidal cell size in postmortem tissue (e.g., Sweet et al., 2004). Interestingly, postmortem studies have yet to show volumetric reductions in HG despite the change in some compartments, suggesting that MR may be detecting changes in tissue parameters that are not apparent in postmortem histological examination. This study also complements a recent diffusion tensor imaging (DTI) study that showed correlations between white matter changes in auditory projection pathways and auditory processing deficits in schizophrenia (Leitman et al., 2007). The relationship between white matter and grey matter pathology requires further investigation.
There are additional lessons hidden in the Salisbury et al. study. Given the relationship between reduced MMN generation (a functional measure) and cortical volume (a structural measure), there is a strong tendency to assume that structural changes are the cause of functional changes. The findings by Salisbury et al., as well as the extrapolation to postmortem histological studies, argue strongly against such an interpretation. For example, in the Salisbury et al. study, the change in left HG volume from time 1 to time 2 was only 6 percent, whereas MMN declined by 33 percent over the same period of time. At time 2, HG volumes were only 2 percent smaller in schizophrenia patients vs. controls, whereas MMN was 35 percent smaller. These findings suggest that simple volume loss does not cause the reduction in MMN. Further, even though MMN reduction seems to stabilize following the first 1.5 years (e.g., Umbricht et al., 2006; Javitt et al., 1995), this may not be the case with volumetric deficits. Thus, in a prior sample of chronic patients, this same group reported reductions of 13 percent in HG volume (Hirayasu et al., 2000), as opposed to the 2 percent reduction observed in patients following 1.5-year follow-up. Rather than suggesting a primary role of degeneration, this suggests a “use it or lose it” relationship within auditory cortex, wherein persistent reduction of activity may lead over time to structural involution. Even in postmortem studies (e.g., Sweet et al., 2004), pyramidal cell volumes are reduced by only 10 percent, whereas MMN in chronic schizophrenia may be reduced by 40 percent or more (e.g., Salisbury et al., 2002; Umbricht et al., 2006).
As noted by Salisbury et al., acute treatment with NMDA antagonists leads to reduced MMN amplitude in both human (Umbricht et al., 2000) and animal (Javitt et al., 1996) models. NMDA receptors also play a critical role in synaptic spine development and maintenance (Matsuzaki et al., 2004). A possible explanation, therefore, is that reduced NMDA activity in auditory cortex leads to both MMN reductions and reductions in spine density. Alternatively, primary alteration in subpopulations of cortical glutamatergic cells could trigger the sequence of events leading to reduced MMN generation.
There are several other intriguing features to the dataset. For example, at baseline, there were several controls who had larger than median HG volumes, but nevertheless failed to generate MMN (i.e., <1 μV). In schizophrenia patients, this sector of the plot was entirely empty and the only subjects who failed to generate MMN were those with small HG volumes. This suggests that there may be fundamental differences in structure/function relationships. It is almost as interesting to know why some controls fail to generate MMN despite having adequate HG size, as it is to know why HG is reduced in schizophrenia.
The finding that the relationships hold only for left, not right, HG, also is worthy of further investigation, as is the finding that right HG volumes are reduced even at first episode and do not decline further. Finally, the correlation on reduced MMN amplitude at Fz with reduced HG volume reiterates once again the role of auditory, rather than frontal, cortices in mediating MMN generation deficits in schizophrenia.
View all comments by Dan Javitt
Related News: Schizophrenia and Neurodegeneration—Case Bolstered by MRI, Electrophysiology
Comment by: Lei Wang
Submitted 5 June 2007
Posted 5 June 2007
The authors reported a cross-sectional (first hospitalization or within 1 year of first hospitalization) and longitudinal (1.5-year follow-up) study of electrophysiologic testing (mismatch negativity, or MMN, amplitude) and high-resolution structural magnetic resonance imaging of Heschl gyrus and planum temporale gray matter volumes. Schizophrenia subjects showed longitudinal volume reduction of left hemisphere Heschl gyrus (P = .003), which was highly correlated with MMN reduction (r = 0.6; P = .04). The interrelated progressive reduction of functional and structural measures suggests progressive pathologic processes early in schizophrenia. The design of the study helped minimize the effect of medication, the authors commented, therefore allowing the interpretation that brain change is due to disease progression.
From an imaging perspective, this is a straightforward longitudinal study of brain structure following previously published image processing and measuring protocols (Kasai et al., 2003). T1- and T2-weighted MR scans were acquired using the same sequence and on the same scanner for all subjects and at all time points. All baseline and follow-up MR scans were bias-field corrected and used in a fully automated segmentation algorithm for tissue classification, and then realigned to standard coordinate space and re-sampled to isotropic voxel resolution for application of standard manual segmentation protocols. Intracranial content was also estimated. Inter-rater and intra-rater reliability for segmentation of the Heschl gyrus and planum temporale was very high (volume ICC ranging from 0.95 to 0.99) (Kasai et al., 2003).
The authors showed in their earlier paper (Kasai et al., 2003) that using this approach, the time-dependent change in the volume of intracranial content did not correlate with time-dependent volume changes of brain structures. While this is reassuring, a trend-level decrease of intracranial content in time (p = 0.065), however, does raise the possibility of some systematic bias such as scanner drift resulting in global scaling, especially considering the subjects’ ages of 21-24 years. Some solutions such as scaling the follow-up scans with respect to the baseline scans could be evaluated (Freeborough and Fox, 1997).
This well-designed and well-presented study adds to a growing body of evidence that longitudinal structural neuroimaging is an effective way to detect progressive changes in specific brain structure in patients with schizophrenia. The results of this study contribute to the debate over whether the pathogenesis of schizophrenia includes a neurodegenerative as well as neurodevelopmental component.
View all comments by Lei Wang
Related News: Schizophrenia and Neurodegeneration—Case Bolstered by MRI, Electrophysiology
Comment by: Robert McClure (Disclosure)
Submitted 10 June 2007
Posted 10 June 2007
Longitudinal increases in volume of the lateral ventricles and decreases in brain volume—progressive changes—are often observed over time early in the course of schizophrenia. There is not uniform agreement over the proper interpretation of these changes, prompting vigorous, healthy debate among investigators. A major point of contention appears to be whether these volume changes actually constitute evidence of active disease progression.
In the current study, the authors seek to bolster the case for structural progression by demonstrating evidence of interrelated progressive functional impairment. They buttress the case for structural progression by demonstrating a relationship between worsening deficit in mismatch negativity and auditory cortex volume decreases.
Identification of a direct causal relationship between the underlying pathophysiology of schizophrenia and volume losses observed early in the illness would conclusively demonstrate structural progression. Such a direct link has not yet been established, so the results of this study constitute only indirect evidence that structural progression is tied to the emergence of functional impairment. Results of longitudinal MRI studies are useful for identify factors potentially associated with these volume changes, including altered neurodevelopment, disease progression, mismatch negativity, antipsychotic medications, and yet unidentified factors. Until the underlying etiology of schizophrenia is known, what underlies longitudinal volume change in schizophrenia is unlikely to be determined.
Future research should focus on specifying the neurodevelopmental mechanisms that contribute to the cortical pathology central to schizophrenia.
View all comments by Robert McClure
Related News: In Pursuit of Positive ID for Schizophrenia Prodrome—A Research Roundup
Comment by: Patricia Estani
Submitted 31 May 2008
Posted 31 May 2008
I recommend the Primary Papers