Psychiatrie Bulletin (1989), 13,702

Conference report
First World Congress on Psychiatrie Genetics
Cambridge, 3-5 August 1989
MICHAELMORRIS,Research Senior Registrar, Institute of Medical Genetics, University of

Wales College of Medicine, Cardiff CF4 4XN; and S. J. ADAMS,Lecturer, Academic
Department of Psychiatry, St Bartholomew's Hospital, London EC1A 7BE

This conference was organised by the Biological Psy
chiatry Group of the College under the auspices of the
World Federation of Societies of Biological Psy
chiatry with Dr T. J. Crow as Chairman of the Organ
ising Committee. The meeting was attended by 270
participants from 25 countries. The 150oral and pos
ter presentations, many of which reported on the ap
plication of recombinant DNA techniques to psy
chiatry, reflected a growing field of intensive research.

The main focus of the meeting was on the genetics
of depression and schizophrenia. It is well-known
that a locus for bipolar affective disorder has been
implicated on chromosome 11in one Amish family in
a study by Professor Janice Egeland et al. However,
re-analysis of the data, updated psychiatric status
and extensions of the core pedigree have shown that
genetic linkage is not as close as was originally
reported. Other centres have not replicated the
original finding of linkage to chromosome 11p 15.

Dr Hugh Gurling presented data showing that a
schizophrenia susceptibility locus may lie on the
proximal long arm of chromosome 5 (5q 11.2-13.3) in
seven British and Icelandic families. However, nega
tive studies from various parts of the world were
reported (Scotland, Wales, Ireland, USA, Canada,
Italy). Evidence supportinga locus for psychosis in the
pseudo-autosomal region of the sex chromosomes
was presented by the Northwick Park Hospital group.
The D2-dopamine receptor gene has been recently
cloned and this gene has been linked to chromosome
11. However, strong evidence against linkage of the
D2 gene to schizophrenia was presented in a large
Swedish kindred.

The great difficulties of research in psychiatric
genetics were debated. Segregation studies have
suggested that genetic models for psychiatric dis
orders such as schizophrenia are complex and the
pattern of inheritance is often unknown. There
fore lod scores, which are usually applied to single
locus models, must be interpreted cautiously.
Other problems are genetic heterogeneity, the
presence of phenocopies (non-genetic alterations
of the phenotype), diagnostic validity and non-
random mating (for example, schizophrenic suf
ferers differentially mate with 'alcoholics'). Yet more

problems are reduced penetrance, variable age of

onset and environmental factors such as life events.
Many strategies for future research were proposed.

There should be a high threshold for definition of a
case. More families should be recruited and other
areas of the genome should be examined for linkage.
New linkage programmes should be developed to
allow for non-Mendelian forms of inheritance. In the
affected sib-pair method of analysis, for example, no
model of inheritance is specified.

Several other neuropsychiatrie diseases were dis
cussed. Closer probes than G8 have been discovered
to be linked to Huntington's disease and preliminary

reports of the clinical application of such probes
in predictive testing were presented by several
centres (Baltimore, Cardiff, Manchester). Regarding
Tourette syndrome, pedigrees of the disorder from the
Middlesex Hospital are consistent with autosomal
dominant inheritance and a locus on chromosome 18
is under investigation. St George-Hyslop's finding
that the genetic defect causing familial Alzheimer's

disease maps on chromosome 21 has been replicated
at St Mary's Hospital, London. Mental handicap

and the molecular study of a fragile site at Xq27.3
are sources of vigorous investigation. The gene for
arylsulfatase A (deficiency of which leads to meta-
chromatic leucodystrophy, a recognised cause of
psychosis and mental retardation) has been cloned in
Germany and this should facilitate the study of
genotype-phenotype relationships. Data on the
genetics of narcolepsy showed that it has the tightest
HLA linkage of any disease (99% of all subjects with
narcolepsy and cataplexy are DR 2 positive). There is
suggestive evidence that there is linkage between al
coholism and the MNS blood group on chromosome
4. Current research indicates that infantile autism is
genetically heterogeneous. Professor Andreas Rett,
who described the eponymous Rett's syndrome in

1966, gave an account of the profound mental and
physical handicaps associated with this disorder.

An important session was held on the ethical and
social implications of molecular and clinical psychi
atric genetics. These include problems associated with
confidentiality and informed consent. The contro
versial subject of carrier detection was debated but the
possibility of applying presymptomatic and prenatal
tests in disorders such as schizophrenia is remote.

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