Psychiatric Genetics and
Genomics is a carefully-selected compilation of chapters that give the
clinician a thorough overview of the influence of recent genetic advances in a
variety of areas, including mental illness, the formation of personality, the
development of learning disorders, and degree of susceptibility to drug and
alcohol addiction.  The tailoring of drug regimens based on individual genetics
is discussed, and implications for medical ethicists are considered.

The heritability (degree of genetic
influence) of serious mental illnesses such as bipolar disorder and
schizophrenia will be of special interest to those who work directly with such
clients.  One of the first questions professionals are asked by the anxious
families of people recently diagnosed with a severe mental illness are, Why has
this happened to us?  Was it the way we treated her as a child?  Were we too
critical, demanding, demeaning, or rejecting? Could it have been that fall from
the tree at age eleven, or that blow to the head during a ninth grade soccer
match?  Or the case of measles mom came down with when she was pregnant? 
Perhaps it’s in the bloodline — there was that other family member, a
grandparent or aunt, rumored to have spent years sequestered away in a mental
hospital long ago.  And if this mental disorder was really caused by some
genetic malfunction, should we worry about the other kids?  Are they also at
risk of developing a terrible illness?  Is there another time bomb yet in store
for the family?

Experienced clinicians are
appropriately cautious in responding to these questions.  The family can safely
be told that not even the experts know how to fully account for or predict
serious mental illnesses.  There has not been much research support for those
once-ubiquitous reports of the psychological damage caused by "schizophrenogenic"
parents, whose emotional mistreatment of the child was thought to be the cause
of schizophrenia.  And as studies of identical twins show, neither can genetics
alone explain the onset of serious mental illnesses.  The best current
understanding is that although the child may have inherited or acquired the
susceptibility for these illnesses, unpredictable environmental factors also
likely play a large role.  So while the family can be reassured that it should
not blame itself, not any more than a family should hold itself responsible
when its members are victims of natural disasters, questions about heritability
and environment remain.

Psychiatric Genetics and
Genomics is divided into four parts.  The first deals with the basic
science of heredity.  This section reviews what is currently known about the
structure and function of DNA, chromosomal abnormalities, and the methods of
quantitative genetics (such as family and twin studies), and establishes
heritability and its analysis as central among the core issues of behavioral
genetics.  Much more compact than a college text, this section is nonetheless
quite thorough and especially useful for clinicians who do not often deal with
these issues at a detailed level.

The second part of this collection
considers both normal and abnormal developmental issues, including personality
formation, the heritability of cognitive capacities, mental retardation and
learning disorders.  A brief history of the quantification of personality is
provided, with special consideration of what is commonly known as the Five
Factor Model of personality.  Although self-report questionnaires form the
basis of most research into personality, twin studies using peer-rating systems
have provided additional support to the (rather consistent) finding that
between 40 and 50 percent of the variability in personality is heritable, and
that the effects of shared environment is negligible.  (The influence of
non-shared environmental factors is substantial, however, accounting for as
much as 50 percent of the variability of personality.  The book’s discussion of
the importance of these non-shared environmental effects is convincing.)

Most researchers now accept the
broad heritability of cognitive capacities, including those abilities that are
assumed to be the basis for general intelligence, or g.  "Correlations
for first-degree relatives living together average 0.43 for more than 8000
parent-offspring pairs and 0.47 for more than 25,000 pairs of siblings"
(p. 83).  Simple cultural and environmental explanations of the correlations
among related family members are unlikely to be correct, since twin studies in
a wide variety of countries, regions and cultures tend to support the heritability
of g.  Of special interest are the studies of twins raised apart, since
this permits substantial isolation of the effects of shared environment.

The third part of this book
considers the possibility of genetic influences on both the mental disorders
widely considered endogenous (e.g., schizophrenia and recurrent major
depression) and those thought to be in large part socially created.  For
example, the heritability of personality factors has recently been fairly well
established, and so the question of genetic underpinnings of personality
disorders also arises.  Many theorists and clinicians have long been assumed
these disorders to be largely the result of environmental deficits or insults. 
For example, borderline personality disorder has been thought to result from an
impaired maternal relationship during infancy and early childhood, and
criminals with diagnosable antisocial personalities are often reported to have
had childhood histories of abuse and neglect.  While research results are
mixed, this book summarizes an assortment of credible studies in the U.S. and
other countries that, on the whole, suggest at least some degree of
heritability in these and other personality disorders.

As pointed out above, the genetic
links in major mental illnesses and vulnerability to substance abuse and misuse
have long been suspected.  There have of course been false starts and overly
optimistic reporting in the media on some lines of promising research, but with
advances in genetic research, scientists are now able to begin the process of
identifying the specific genes that may be involved in the development of many
of these disorders.  Once these genes have been identified, animal studies can
be designed to allow better-controlled experimentation on these illnesses and
conditions.

The last section of the book is
composed of chapters on psychopharmacogenetics, ethics related to genetics
research and applied science, the counseling of people in whom genetic
susceptibilities have been identified, and the future of psychiatry and
psychology after the promises of genetic research have been more fully
realized.

Although some sections of this book
will be somewhat stiff reading for those without scientific training, most of
this material should be accessible to scientists and practitioners alike.

© 2003 Keith
Harris

Keith Harris, Ph.D.,
is a clinical psychologist and supervises the research section of the
Department of Behavioral Health, San
Bernardino County, California. His
interests include the empirical basis for psychotherapy research (and its
design), human decision-making processes, and the shaping of human nature by
evolutionary forces.

Categories: Genetics, MentalHealth