Table 1.
Commonalities and differences between randomized controlled trial (RCT) and naturalistic study designs.
| Study Design | RCT | Naturalistic Study Design |
| Ecological validity | Low to medium | High |
| External validity | Low to medium | High |
| Internal validity | High | Low to medium |
| Criterion validity | High | High |
| Construct validity | High | High |
| Screening | Controlled, per protocol | Controlled, per protocol |
| Inclusion, exclusion criteria | Yes | Yes |
| Familiarize with procedures and tests | Yes | Yes |
| Drinking session | Per protocol, supervised | Uncontrolled, not supervised |
| Instructions | Per protocol | None, or minimal |
| Amount, type of drink | Pre-set, standardized | Self-initiated |
| Start and stop time of drinking | Pre-set, per protocol | Self-initiated |
| Behaviors during drinking | Restricted, per protocol | Free (as normal) |
| Drinking environment | Research unit | Free (e.g., bar(s), at home) |
| Social aspects of drinking (if not alone) | With strangers | With friends or strangers |
| Real time assessments (e.g., BAC) | Yes | Possible via mobile technology |
| Food and water intake | Restricted, per protocol | Free (as normal) |
| Smoking | Restricted, per protocol | Free (as normal) |
| Sleep | Controlled and supervised | Uncontrolled, not supervised |
| Time to bed, wake up time | Restricted, per protocol | Self-initiated |
| Sleep hygiene and related behaviors | Restricted, per protocol | Self-initiated |
| Monitoring, real time assessments | Yes | Possible via mobile technology |
| Sleep environment | Sleep unit | At home or elsewhere |
| Test days | Controlled and standardized | Controlled and standardized |
| Psychometric tests, mood assessments | Standardized and validated | Standardized and validated |
| Time of testing | Per protocol at pre-set time | Per protocol at pre-set time |
| Conductance of study procedures | Per protocol | Per protocol |
| Supervision, monitoring | Yes | Yes |
Description of validity types: Ecological validity = to what extend the study reflects a realistic hangover drinking occasion; external validity = to what extent can findings be generalized to the population as a whole; internal validity = to what extent can the design demonstrate causal effects; criterion validity = to what extent are measures related to study outcomes; construct validity = the degree to which the administered tests measure what they claim or purport to be measuring. Abbreviation: Blood alcohol concentration (BAC). Please note that this table is intended to contrast the RCT and naturalistic study design. Some studies might incorporate features of both designs (e.g., supervised and standardized alcohol administration, but unsupervised sleep at home). Additionally, studies with the same design type may differ significantly in the levels of control, standardization, and quality.