1.A.1
Biological bases: genes, brain systems, drugs and imaging
ASPPB's competency statement 1.A.1: Biological bases of behavior (e.g., genetics, neurobiology, psychopharmacology, brain imaging)
This statement covers how genes, the nervous and endocrine systems, psychoactive drugs and brain imaging relate to behavior. Few psychologists prescribe, but most work with clients who take medication, read imaging studies and hear claims that a problem is 'genetic'. Knowing what each kind of biological evidence can and cannot show keeps a formulation accurate, signals when to involve a prescriber or physician, and guards against both overstating and dismissing biological findings.
Key ideas
- Heritability
- The share of variation in a trait, within a particular population and environment, that goes with genetic differences among its members. It is a population statistic: it does not say how much of one person's trait comes from genes, and a heritable trait can still change with the environment.
- Stress hormones (HPA axis)
- The hypothalamus, pituitary and adrenal cortex form a hormonal chain that ends in cortisol, which feeds back to switch the response off. Brief activation is protective; prolonged or poorly regulated activation adds to the cumulative wear on the body that McEwen called allostatic load.
- Drug action at receptors and transporters
- Many psychoactive drugs act on receptors or transporters. The clinical potency of older antipsychotics tracks how strongly they bind dopamine receptors, and selective serotonin reuptake inhibitors (SSRIs) occupy the transporter that clears serotonin from the synapse.
- Withdrawal and tapering
- The brain adapts to a drug taken for months, so stopping suddenly can cause withdrawal symptoms. After SSRIs these typically begin within a few days, are easily mistaken for relapse, and are reduced by a gradual taper planned with the prescriber.
- Imaging methods
- Structural imaging shows anatomy; functional methods track activity. Functional magnetic resonance imaging (fMRI) measures blood flow and oxygenation changes, an indirect signal with high spatial resolution, while electroencephalography (EEG) measures neural electrical activity directly, with high temporal resolution but coarse localization.
Worked example
A client who has taken an SSRI for eight months tells her psychologist she feels well and will stop the medication this weekend, without telling the family physician who prescribed it. She adds that if she feels dizzy or irritable afterward, that will prove her depression is back.
- Name the biological issue: after months of use the brain has adapted to the drug, so stopping abruptly can bring withdrawal symptoms such as dizziness and irritability.
- Correct her inference: withdrawal symptoms usually start within a few days of stopping and are easily mistaken for relapse, so feeling unwell soon after a sudden stop would not by itself show that the depression has returned.
- Stay within competence: the psychologist does not set a dose schedule but encourages her to talk with the prescriber first, since a slow, planned taper reduces withdrawal symptoms.
- Offer collaboration: with her consent, share relevant observations with the physician and track mood and possible withdrawal symptoms during any taper, so the two can be told apart.
Knowing how drugs act on the brain lets a psychologist give accurate information while leaving prescribing decisions with the prescriber.
Check yourself
A researcher wants to know which brain regions respond more strongly when adults with obsessive-compulsive disorder view contamination images than when they view neutral images. Which method best suits this question?
Sources
- Visscher, Hill and Wray (2008), Heritability in the genomics era: concepts and misconceptions, Nature Reviews Genetics (PMID 18319743), Abstract; definition of heritability as a population parameter
- McEwen (1998), Protective and damaging effects of stress mediators, New England Journal of Medicine (PMID 9428819), Whole article: stress mediators, allostasis and allostatic load
- Creese, Burt and Snyder (1976), Dopamine receptor binding predicts clinical and pharmacological potencies of antischizophrenic drugs, Science (PMID 3854), Abstract
- Horowitz and Taylor (2019), Tapering of SSRI treatment to mitigate withdrawal symptoms, Lancet Psychiatry (PMID 30850328), Abstract: withdrawal mistaken for recurrence; serotonin transporter occupancy; gradual tapering
- Fava, Gatti, Belaise, Guidi and Offidani (2015), Withdrawal symptoms after selective serotonin reuptake inhibitor discontinuation: a systematic review, Psychotherapy and Psychosomatics (PMID 25721705), Abstract, Results and Conclusions: onset within a few days; misidentified as relapse
- Mulert (2013), Simultaneous EEG and fMRI: towards the characterization of structure and dynamics of brain networks, Dialogues in Clinical Neuroscience (PMID 24174908), Abstract: EEG direct with high temporal resolution; fMRI indirect, hemodynamic, high spatial resolution
- Logothetis (2008), What we can do and what we cannot do with fMRI, Nature (PMID 18548064), Abstract; the hemodynamic signal and its limits
- Shearer, Moore, Comaty and colleagues (2026), Practice guidelines regarding psychologists' involvement in pharmacological issues (APA revision approved August 2025), American Psychologist (PMID 42295216), Executive summary: collaboration with medical providers
- American Psychological Association (2017), Ethical Principles of Psychologists and Code of Conduct, Standard 2.01, Boundaries of Competence