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Chapter 28: Psychotherapies
Table 28.14-1
Genetic Terminology
Absolute risk
One’s risk of developing a disease over a specified time period (e.g., the empirical risk for autism in a sibling
of an individual with idiopathic autism is about 6%–8%; related term: relative risk)
Allele
One of the variant forms of a gene at a particular locus, or location, on a chromosome
Assortative mating
Nonrandom mating in which individuals preferentially mate with others with similar traits
Consultand
Person seeking genetic counseling
Complex (or
multifactorial)
Traits, diseases, or disorders resulting from the interactions of genetic and environmental factors
Familial
Disorder recurring in a family that may result from a combination of shared genotype and environment
First-degree relatives
Biological relatives sharing 50% of their genetic makeup (e.g., parents, siblings, children)
Gene of major effect
As found in true dominant and recessive genetic disorders, a gene that is able independently to cause a
phenotype, with little influence from the environment or other genetic contributions
Genome
All of the DNA (deoxyribonucleic acid) within a cell or organism; nuclear and mitochondrial
Genotype
Genetic makeup; most often referring to the allelic contribution at a particular locus
Heritability
Proportion of phenotypic variance attributable to genetic variance
Morbid or lifetime risk The probability that subjects under study will develop an illness if they live long enough; takes into
consideration that a susceptible subject may not have onset at the time of examination or may die of
another cause before onset
Phenotype
Clinical presentation of the disorder
Polygenic
Traits resulting from the interaction of multiple genes
Presymptomatic
Unaffected individual known to carry a mutation that is very likely to result in the expression of the
disorder
Proband
The affected person bringing the family to medical attention
Recurrence risk
Probability that a disorder will recur in other family members
Relative risk
One’s risk of developing a disease when compared with a referent group (e.g., if the probability of developing
idiopathic autism among siblings of an affected person is 6%–8% compared with the risk in the general
population of 0.1%, then the relative risk of autism in siblings of an affected individual is about 70; related
term: absolute risk)
Second-degree
relative
Biological relatives sharing 25% of their genetic makeup (e.g., grandparents, grandchildren, nephews, nieces)
Susceptibility
Increased risk, owing to the presence of deleterious allele, of developing a disease or disorder compared with
the general population
Spectrum disorders
Disease or disorders in which the phenotypic expression is characterized by a broad range of variance (e.g.,
autism spectrum disorders)
Table 28.14-2
Examples of Psychiatric Disorders Recognized as
Having a Genetic Component to Their Etiology
Psychotic disorders: Schizophrenia, schizoaffective disorder
Mood disorders: Bipolar disorder, recurrent unipolar depression
Personality disorders: Antisocial personality disorder, schizotypal
disorder
Anxiety disorders: Generalized anxiety disorder, obsessive-
compulsive disorder, panic disorder, phobia
Substance-related disorders: Substance dependence and abuse
Eating disorders: Anorexia nervosa, bulimia
Childhood disorders: Attention-deficit/hyperactivity disorder,
autism, chronic tic disorders, including Tourette’s disorder
Memory disorders: Alzheimer’s disease
phenotype level. If all individuals who carry the dominant gene show
any phenotype of the gene, the gene is said to be
completely penetrant.
Currently, only rare examples exist of known genes for mental disorders
that demonstrate complete penetrance of symptoms in the presence of a
single gene. One such example is early-onset familial Alzheimer’s dis-
ease resulting from mutations in the amyloid precursor protein (APP)
located on the long arm of chromosome 21. In contrast,
expressivity
refers to the extent to which a genotype is expressed. In the case of vari-
able expressivity, the trait can vary in expression from mild to severe,
but is never completely unexpressed in individuals who have the gene.
The genes that result in most mental disorders are believed to regulate
a wide spectrum of traits demonstrating variability of expression (spec-
trum disorders).
Components of the Genetic
Counseling Process
Requests for genetic counseling are often initiated by the cli-
ent’s or relatives’ questions about the disorder that is present in
the family. In the case of mental illness, the questions are often
posed to the treating psychiatrist. The client’s questions are most
effectively addressed through an interactive process that provides
the client, as well as the professional, with information pertinent
to the next step in the communication process. The basic compo-
nents of genetic counseling are outlined in Table 28.14-3.
Contracting
Contracting is a vital portion of the psychiatric genetic counseling
session. Often the goals of the session will vary based on the con-
sultand’s histories and reason(s) for concern. The provider should work
with the consultand at the beginning of the session to define mutual
goals.
