Kaplan + Sadock's Synopsis of Psychiatry, 11e

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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 Nonrandom mating in which individuals preferentially mate with others with similar traits

Assortative mating

Consultand Complex (or

Person seeking genetic counseling

Traits, diseases, or disorders resulting from the interactions of genetic and environmental factors

multifactorial)

Familial

Disorder recurring in a family that may result from a combination of shared genotype and environment Biological relatives sharing 50% of their genetic makeup (e.g., parents, siblings, children) 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 All of the DNA (deoxyribonucleic acid) within a cell or organism; nuclear and mitochondrial

First-degree relatives Gene of major effect

Genome Genotype Heritability

Genetic makeup; most often referring to the allelic contribution at a particular locus

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 Susceptibility

Biological relatives sharing 25% of their genetic makeup (e.g., grandparents, grandchildren, nephews, nieces)

Increased risk, owing to the presence of deleterious allele, of developing a disease or disorder compared with the general population Disease or disorders in which the phenotypic expression is characterized by a broad range of variance (e.g., autism spectrum disorders)

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.