Mohammed T. Abou-Saleh

494 PRINCIPLES AND PRACTICE OF GERIATRIC PSYCHIATRYMorrissey 18 described a syndrome of paranoid delusions andhallucinations in the context of preserved intellect, personalityand affect. Because of the phenomenological similarity to Kraepelin’s‘‘paraphrenia’’ and due to its late onset, Roth and colleaguestermed this disorder ‘‘late paraphrenia’’ 19,20 , a name that wasdesigned to encompass all late-onset, non-affective, non-organicpsychoses in which paranoid symptoms were prominent. Thus,the term was both broader than late-onset schizophrenia, in that itencompassed late-onset delusional disorder, and more restrictive,in that it did not include non-paranoid forms of late-onsetpsychosis. Post 21 developed a different descriptive system. Hedivided late-onset (after age 50) psychoses into paranoid hallucinosis,schizophreniform syndrome, and schizophrenic syndrome.Based on a 3 year follow-up, however, he concluded that thesethree diseases were actually a continuum of the same disorder withslightly different symptom profiles.European debates and developments were slow to influencethe classification system used in the USA. The first Diagnosticand Statistical Manual of the Mental Disorders (DSM-I) 22 usedthe term ‘‘involutional psychotic reaction’’, which encompassedboth paranoid ideation and depression in older patients. Thisamalgam of affective and psychotic symptoms in the elderly wassplit in the second edition (DSM-II) 23 in favor of ‘‘involutionalparanoid state (involutional paraphrenia)’’ and ‘‘involutionalmelancholia’’. The former disorder, like Roth’s late paraphrenia,was characterized by ‘‘delusion formation with onset in theinvolutional period . . . The absence of conspicuous thoughtdisorders typical of schizophrenia distinguishes it from thatgroup’’ 23 . Schizophrenia could be diagnosed in individuals withany age of onset.1970–PRESENTAs European psychiatrists began to study patients with lateparaphrenia more systematically, new classification systems in theUSA were restricting the diagnosis of late-onset psychosis. One ofthe five Feighner Research Criteria 24 for schizophrenia was age ofonset before age 40. In the third edition of the DSM (DSM-III) 25 ,a diagnosis of schizophrenia could not be made if the onset ofsymptoms was after age 45. Late-onset psychosis that involvedpersistent persecutory delusions with prominent hallucinationscould be given a diagnosis of ‘‘paranoid disorder’’. This classificationsystem was in stark contrast to both earlier RDC criteria 26and to the 9th version of the International Classification ofDiseases (ICD-9) 27 , neither of which imposed age-of-onset restrictionsfor schizophrenia. The ICD-9 also allowed for a diagnosis ofparaphrenia at any age. The revised version of DSM-III (DSM-III-R) 28 rectified the omission of late-onset schizophrenia byproviding a separate diagnostic category for those diagnosed withschizophrenia after age 45. In the most recent version of the DSM(DSM-IV) 29 and the ICD (ICD-10) 30 , no special categories existfor late-onset psychoses, although schizophrenia may be diagnosedat any age.TOWARD A CONSENSUSIt is clear from this historical review that there has been littleconsensus regarding the classification of late-onset non-affectivenon-organic psychoses. Two opposing lines of thought havepulled the terminology in different directions. On the one hand,some authors have preferred to emphasize the similarity of lateonsetpsychoses to the corresponding early-onset disorders. Thishas resulted either in the use of terms such as ‘‘late-onsetschizophrenia’’ and ‘‘late-onset delusional disorder’’ or hasprompted a move toward ignoring age of onset altogether inclassification (e.g. DSM-IV, ICD-10). On the other hand, somemembers of the psychiatry community (mainly those in the UK)have preferred to emphasize differences between the phenomenologyof late- and early-onset psychosis and thus have tended to usedistinct terminology, such as ‘‘paraphrenia’’ or ‘‘late paraphrenia’’.Thus, questions remain about which terminology wouldoptimally serve the clinical and research communities. There areat least two overlapping issues to consider. First, how similar ordifferent is the late-onset, non-affective, non-organic psychosisfrom early-onset disorders? If late-onset patients are no differentfrom early-onset patients in terms of demography, phenomenology,etiological factors, prognosis and treatment, then it would beredundant to classify them in a separate category. If, however,such features differ between early-onset and late-onset individuals,then it would seem important to preserve a distinct diagnosticcategory in order to encourage further research and allow foroptimal prognostic evaluation and treatment. The magnitude orextent of the differences between early- and late-onset individualsshould also influence the terminology chosen for the diagnosticcategorization. If a majority of critical clinical features are sharedwith an early-onset disorder, then it would make sense to adopt aterm such as ‘‘late-onset schizophrenia’’. If the extent ofdifferences is sufficiently large, a separate term would bewarranted. A second issue to consider in determining the bestclassification scheme is what age of onset should be called ‘‘late’’.Most of the American studies of late-onset non-affective, nonorganicpsychosis have included patients with onset after 45 andgenerally before age 65. In addition, among the patients inBleuler’s late-onset schizophrenia studies, only 4% had an onsetafter age 60 7 . In contrast, most studies of late paraphrenia havebeen conducted with patients whose onset was after age 65.Differences in age-of-onset between late-onset schizophrenia andlate paraphrenia studies may help to explain some of thediagnostic confusions that have persisted.Only recently has the weight of evidence become sufficientlygreat in the field of late-life psychoses to allow for adequateconsideration of these issues. In July 1998, the International Late-Onset Schizophrenia Group met to present reviews of publisheddata on late-onset non-affective, non-organic psychosis and todevelop a consensus statement regarding diagnostic categories 2 .The statement recognizes two illness classifications: late-onset(onset after the age of 40 years) schizophrenia and a very-lateonset(onset after 60) schizophrenia-like psychosis. Thus, thegroup determined that it was important to recognize a diagnosticdistinction based on age of onset, due to differences between lateandearly-onset patients, but that the disorders were not sufficientlydifferent to warrant a separate nomenclature. In addition,the group felt that a further distinction was warranted within lateonsetpatients between those with onset in middle age and thosewith very late onset, based on major differences between thesegroups.The similarities and differences among early-onset schizophrenia,late-onset schizophrenia and very-late-onsetschizophrenia-like psychosis are summarized in Table 89.1.There are many areas of similarity between both late-onsetgroups and early-onset schizophrenia, such as symptoms 31–33 ,family history 32 , brain imaging findings 34–36 , and the nature ofcognitive deficits 35 . The decision to retain the word ‘‘schizophrenia’’in the nomenclature of both disorders was driven bythese strong similarities. On the other hand, the consensusstatement’s distinction between those with middle-age-onset andold-age-onset psychoses was motivated by epidemiological,etiological and symptom differences between these two groups.Very-late-onset schizophrenia-like psychosis is different fromboth early- and late-onset schizophrenia, in that these casestend to be associated with sensory impairment and socialisolation 20 , are less likely to exhibit formal thought disorder and