6: intervention studies and group designs

Question 1

Main questions of psychotherapy research

Answer 1

Psychotherapy outcome research: see whether a treatment produces the desired and expected clinical results.

Psychotherapy process research: focus on the process of psychotherapy and its relationship with the outcome. Both qualitative and quantitative.

Question 2

Psychotherapy outcome research

Answer 2

See whether a treatment produces the desired and expected clinical results.

Mostly qualitative approach is used.

Question 3

Psychotherapy process research

Answer 3

Focus on the process of psychotherapy and its relationship with the outcome.

Both qualitative and quantitive methods are used.

Question 4

James Lind

Answer 4

Did one of the first experiments with clinical trials in medicine on scurvy (disease caused by lack of vitamin C).

12 participants - 6 different conditions.

Only condition that worked: eating two oranges and a lemon a day.

BIASES:

• small sample
• no randomization of group
• experimenter may have had a secret favorite treatment.

Question 5

Single-case study

Answer 5

Applying the intervention to a single participant and noting change

Question 6

Strength/weakness of single-case study

Answer 6

S: simple; close to clinical practice

W: Sufficient only if changes in the absence of the intervention are known for certain.

Question 7

Case series

Answer 7

A series of similar clients receive same intervention

Question 8

Strength/weakness of case-series

Answer 8

S: sampling variability is reduced as sample size increase;

W: no explicit comparison with the absence of the intervention

Question 9

Historical controls

Answer 9

Comparing a current cohort, to an earlier cohort before the intervention was available

Question 10

Strength/wekness of historical controls

Answer 10

S: establishes and explicit comparison

W: services and characteristics of the population may have changed

Question 11

Parallel control-matching

Answer 11

Choosing control subjects that are matched on known confounding factors

Question 12

Strength/weakness of parallel control matching

Answer 12

S: rules out historical shifts

W: difficult to achieve balance; impossible to control for unknown confounders

Question 13

Paralell controls randomization

Answer 13

One sample is divided randomly into different interventions

Question 14

Strength/weaknesses of parallel controls randomization

Answer 14

S: can create balance on known and unknown confounders

W: clinicians who make decisions about inclusion will try to undermine random assignment

Question 15

Parallel control randomization with allocation concealment

Answer 15

Randomization sequence is kept concealed from clinicans

Question 16

Strength/weakness of parallel control randomization with allocation concealment

Answer 16

S: creates balance on known and unknown confounders, preventing subversion

W: clinicians may still attempt to guess the next assignment

Question 17

Key design features in clinical trials

Answer 17

• Explicit inclusion and exclusion criteria (sampling)
• Control conditions
• Randomization
• Blinding or allocation concealment
• Outcome measures are standardized

Question 18

Threats to internal validity in clinical trials

Answer 18

Selection bias
Performance bias
Detection bias
Allegiance bias
Attribution bias

Question 19

Selection bias

Answer 19

Differences between test and control population regarding their structural compositions. –> randomization

Question 20

Performance bias

Answer 20

Differences in the treatment apart from the intervention tested

happens when one group of subjects in an experiment (for example, a control group or an treatment group) gets more attention from investigators than another group.

Question 21

Detection bias

Answer 21

Differences in observation of outcome parameter

Question 22

Allegiance bias

Answer 22

A researchers belief in the superiority of a treatment can cause indirect systemic bias

Question 23

Attribution bias

Answer 23

Related to differences in dropouts between test and control group

Question 24

Threats to external validity

Answer 24

Process of consenting: patient who give their consent to participate have been proven to differ largely in severity of illness and other parameters to those who do not give their consent.

Consenting and selection criteria:

Question 25

Internal validity

Answer 25

degree to which causality can be inferred

Question 26

External validity

Answer 26

Generalizability over time, setting or person. Irrelevant if internal validity is low

Question 27

Construct validity

Answer 27

therapy should produce the expected outcomes. if a test measure what is supposed to measure.

Question 28

Statistical conclusion validity

Answer 28

Statistical significance vs clinical significance.

Question 29

Focus of research question: Efficacy

Answer 29

The extent to which an intervention produces a beneficial result under ideal condition.
Clinical trials that assess efficacy are sometimes called EXPLANATORY TRIALS.

Question 30

Focus of research question: effectiveness

Answer 30

The extent to which a specific intervention, when used under ordinary circumstances does what is it intended to do.

A measure of how well the treatment works in the real world, with all its limitations.

Question 31

Intention to treat (ITT)

Answer 31

refers to analyzing all participants according to their original group assignment, regardless of what subsequently occurred.

Question 32

Parallell study

Answer 32

Individuals are randomly allocated to one group.

Has at least two groups, but can have several, where one is a control group and the other are interventions groups.

Question 33

Crossover study

Answer 33

Larger control over known or unknown confounders

Question 34

First attempts at “psychotherapy”

Answer 34

• Mentally ill patients were considered weak
• Religious practices were sometimes the best attempts for healing mental diseases
• Exorcism were the only method for treating psychotic states

Question 35

What is psychotherapy?

Answer 35

• interpersonal treatment based on psychological principles and involved a trained therapist and client
• It is intended by the therapist to be remedial for the clients disorder.

Question 36

Two major meta-theories of psychotherapy

Answer 36

• Medical model

- Contextual model

Question 37

Medical model (psychotherapy)

Answer 37

• There are specific therapeutic ingredients necessary for the remediation of a disorder, a problem or a complaint
• Psychotherapy treatment manuals -> standardization of a treatment
• Empirical supported treatments

Question 38

Contextual model

Answer 38

• humans evolved to health through social means
• There are three pathway in which psychotherapy works
• Creation of expectation through explanation of disorder and treatments

Question 39

Efficacy research focus (validity)

Answer 39

high internal and low external validity

Question 40

Effectiveness research focus (validity)

Answer 40

lower internal and higher external validity