Science as Evidence in Clinical Psychology – Workshop 2 Page 1 of 8
1–2. WHY EVIDENCE MATTERS & WHAT IS EVIDENCE-BASED PRACTICE?
Clinical psychology uses evidence to answer three main questions: Evidence-based practice (EBP) means using the best available evidence
Does an intervention work? to decide whether a treatment works, who it works for, and whether it is
How strong is the evidence that it works? appropriate in a particular context. It involves asking:
How should evidence be used in clinical decision-making? Is the treatment effective? For whom? Compared with what?
Clinical psychologists do not just rely on opinion, intuition, or tradition — they Is it better than another option?
evaluate whether treatments are supported by robust research. Is it affordable? Acceptable to the patient?
Key sentence: Evidence is used in clinical psychology to develop, Does it work in real-world settings?
evaluate, and justify interventions, treatments, and therapies.
Good exam wording: EBP involves integrating the best available research
evidence with clinical expertise and patient preferences to guide
treatment decisions.
3. THE SCIENTIFIC APPROACH — EVIDENCE VS OPINION
Evidence should be based on systematic observation, measurement, and Key sentence: The scientific approach aims to test claims rigorously
testing. Opinion may be influenced by personal belief, media exposure, rather than relying on personal belief, intuition, or anecdote.
anecdote, or emotional reasoning.
Who needs evidence?
A scientific approach usually involves:
Patients — to make informed choices about treatment (evidence-based
Asking a clear question; forming a hypothesis
patient choice)
Testing the hypothesis systematically
Practitioners — to avoid relying on intuition, habit, personal preference,
Collecting and analysing data
or outdated training
Considering alternative explanations
Healthcare systems — to decide which services to fund; resources are
Drawing cautious conclusions limited; treatments must be effective and cost-effective
4–5. THE MMR-AUTISM EXAMPLE — WHY EVIDENCE QUALITY MATTERS
A 1998 paper claimed a link between MMR vaccine and autism in 12 Why this matters: Poor-quality evidence can influence public beliefs and
children. The evidence was extremely weak because it was based on: health behaviour even when later discredited. Fear about vaccines can
Very small sample (12 children) reduce vaccination uptake, increasing risk of preventable disease
No control group outbreaks.
Parental recall
What this teaches about evidence: Not all published research is equally
Linked common conditions together
reliable. A study may be published but still have: poor design, small sample,
Poor research design
bias, lack of control group, unreliable measurement, conflicts of interest,
Later concerns about dishonesty and unreliable data inappropriate conclusions.
The paper was later retracted.
Key point: Publication does not automatically mean a claim is
scientifically strong.
Strong exam sentence: The MMR-autism controversy illustrates how weak or misleading evidence can shape public opinion and health behaviour,
highlighting the importance of evaluating methodological quality.
, Science as Evidence in Clinical Psychology – Workshop 2 Page 2 of 8
6–8. EFFICACY VS EFFECTIVENESS
EFFICACY EFFECTIVENESS
Whether an intervention works under ideal, controlled conditions. Whether an intervention works in real-world clinical practice.
Usually means: Usually means:
Highly selected participants; strict inclusion/exclusion criteria More diverse patients; comorbidities
Trained professionals; standardised treatment delivery Less controlled environments; usual clinical staff
Careful monitoring; controlled environment Flexible treatment delivery
Example: A CBT intervention tested in a university research clinic with highly Real-world barriers: dropout, missed appointments, service limitations
trained therapists and carefully selected participants may show high efficacy. Example: CBT-I in an NHS primary care setting where patients vary in age,
Key sentence: Efficacy asks whether an intervention works under ideal severity, motivation, comorbidities, and medication use.
or controlled conditions. Key sentence: Effectiveness asks whether an intervention works in
routine, real-world practice.
Exam-friendly sentence: An intervention may show efficacy in controlled trials but still show weaker effectiveness in routine practice because real-world
patients and services are more complex.
12. THE HIERARCHY OF EVIDENCE — STRONGEST TO WEAKEST
The hierarchy ranks research designs according to their likely risk of bias. Important nuances:
Higher up = more reliable because stronger methods reduce bias.
The hierarchy is a guide, not an absolute rule
1 Systematic reviews & meta-analyses of RCTs Different research questions require different methods
2 Randomised controlled trials (RCTs) RCTs are not always possible, ethical, or necessary
Lower-ranked evidence can still be valuable for generating hypotheses,
3 Cohort studies
understanding complexity, or studying rare conditions
4 Case-control studies
5 Cross-sectional studies / surveys Parachute example: Demonstrates RCTs are not always needed. It would
be absurd and unethical to randomly allocate people jumping from aircraft to
6 Case reports / case studies parachute vs placebo parachute. Sometimes effects are obvious enough that
7 Mechanistic studies RCT evidence is not required.
8 Expert opinion / editorials Key sentence: RCTs are a major source of evidence, but different clinical
9 Anecdotes / testimonials / intuition questions require different research methods.
1–2. WHY EVIDENCE MATTERS & WHAT IS EVIDENCE-BASED PRACTICE?
Clinical psychology uses evidence to answer three main questions: Evidence-based practice (EBP) means using the best available evidence
Does an intervention work? to decide whether a treatment works, who it works for, and whether it is
How strong is the evidence that it works? appropriate in a particular context. It involves asking:
How should evidence be used in clinical decision-making? Is the treatment effective? For whom? Compared with what?
Clinical psychologists do not just rely on opinion, intuition, or tradition — they Is it better than another option?
evaluate whether treatments are supported by robust research. Is it affordable? Acceptable to the patient?
Key sentence: Evidence is used in clinical psychology to develop, Does it work in real-world settings?
evaluate, and justify interventions, treatments, and therapies.
Good exam wording: EBP involves integrating the best available research
evidence with clinical expertise and patient preferences to guide
treatment decisions.
3. THE SCIENTIFIC APPROACH — EVIDENCE VS OPINION
Evidence should be based on systematic observation, measurement, and Key sentence: The scientific approach aims to test claims rigorously
testing. Opinion may be influenced by personal belief, media exposure, rather than relying on personal belief, intuition, or anecdote.
anecdote, or emotional reasoning.
Who needs evidence?
A scientific approach usually involves:
Patients — to make informed choices about treatment (evidence-based
Asking a clear question; forming a hypothesis
patient choice)
Testing the hypothesis systematically
Practitioners — to avoid relying on intuition, habit, personal preference,
Collecting and analysing data
or outdated training
Considering alternative explanations
Healthcare systems — to decide which services to fund; resources are
Drawing cautious conclusions limited; treatments must be effective and cost-effective
4–5. THE MMR-AUTISM EXAMPLE — WHY EVIDENCE QUALITY MATTERS
A 1998 paper claimed a link between MMR vaccine and autism in 12 Why this matters: Poor-quality evidence can influence public beliefs and
children. The evidence was extremely weak because it was based on: health behaviour even when later discredited. Fear about vaccines can
Very small sample (12 children) reduce vaccination uptake, increasing risk of preventable disease
No control group outbreaks.
Parental recall
What this teaches about evidence: Not all published research is equally
Linked common conditions together
reliable. A study may be published but still have: poor design, small sample,
Poor research design
bias, lack of control group, unreliable measurement, conflicts of interest,
Later concerns about dishonesty and unreliable data inappropriate conclusions.
The paper was later retracted.
Key point: Publication does not automatically mean a claim is
scientifically strong.
Strong exam sentence: The MMR-autism controversy illustrates how weak or misleading evidence can shape public opinion and health behaviour,
highlighting the importance of evaluating methodological quality.
, Science as Evidence in Clinical Psychology – Workshop 2 Page 2 of 8
6–8. EFFICACY VS EFFECTIVENESS
EFFICACY EFFECTIVENESS
Whether an intervention works under ideal, controlled conditions. Whether an intervention works in real-world clinical practice.
Usually means: Usually means:
Highly selected participants; strict inclusion/exclusion criteria More diverse patients; comorbidities
Trained professionals; standardised treatment delivery Less controlled environments; usual clinical staff
Careful monitoring; controlled environment Flexible treatment delivery
Example: A CBT intervention tested in a university research clinic with highly Real-world barriers: dropout, missed appointments, service limitations
trained therapists and carefully selected participants may show high efficacy. Example: CBT-I in an NHS primary care setting where patients vary in age,
Key sentence: Efficacy asks whether an intervention works under ideal severity, motivation, comorbidities, and medication use.
or controlled conditions. Key sentence: Effectiveness asks whether an intervention works in
routine, real-world practice.
Exam-friendly sentence: An intervention may show efficacy in controlled trials but still show weaker effectiveness in routine practice because real-world
patients and services are more complex.
12. THE HIERARCHY OF EVIDENCE — STRONGEST TO WEAKEST
The hierarchy ranks research designs according to their likely risk of bias. Important nuances:
Higher up = more reliable because stronger methods reduce bias.
The hierarchy is a guide, not an absolute rule
1 Systematic reviews & meta-analyses of RCTs Different research questions require different methods
2 Randomised controlled trials (RCTs) RCTs are not always possible, ethical, or necessary
Lower-ranked evidence can still be valuable for generating hypotheses,
3 Cohort studies
understanding complexity, or studying rare conditions
4 Case-control studies
5 Cross-sectional studies / surveys Parachute example: Demonstrates RCTs are not always needed. It would
be absurd and unethical to randomly allocate people jumping from aircraft to
6 Case reports / case studies parachute vs placebo parachute. Sometimes effects are obvious enough that
7 Mechanistic studies RCT evidence is not required.
8 Expert opinion / editorials Key sentence: RCTs are a major source of evidence, but different clinical
9 Anecdotes / testimonials / intuition questions require different research methods.
