Table 2.
Descriptive statistics of neuropsychological composite variables by group
| Controls (n = 34)
|
Marijuana users (n = 31)
|
||||
|---|---|---|---|---|---|
| Composite variablesa Testsb | M (SD) | Range | M (SD) | Range | Cronbach’s αc |
| Psychomotor Speedd | 0.06 (0.89) | −1.98–1.49 | −0.09 (0.78) | −2.59–1.02 | .57 |
| D-KEFS Trails Number Sequencing (SS) | 11.2 (2.8) | 1–15 | 10.8 (2.5) | 1–14 | |
| D-KEFS Trails Letter Sequencing (SS) | 11.2 (2.8) | 3–15 | 10.7 (2.6) | 3–14 | |
| Visuospatial Function and Memory | −0.09 (0.76) | −1.31–1.58 | 0.12 (0.78) | −1.71–1.53 | .65 |
| Rey-Osterrieth Copy Accuracy (raw) | 29.3 (3.4) | 23.0–34.0 | 30.9 (2.9) | 24.5–35.0 | |
| Rey-Osterrieth Delay Accuracy (raw) | 18.4 (4.1) | 9.0–29.0 | 19.5 (5.7) | 5.0–29.0 | |
| WASI Block Design (SS) | 58.1 (5.7) | 44–67 | 57.9 (6.3) | 47–67 | |
| Complex Attentiond | 0.04 (0.63) | −1.31–0.83 | −0.04 (0.68) | −1.44–1.43 | .73 |
| CVLT-II Trial 1 (Z score) | −0.18 (0.09) | −2.0–3.0 | −0.55 (0.6) | −2.0–2.0 | |
| D-KEFS Letter Fluency Total Correct (SS) | 12.2 (2.2) | 8–17 | 13.2 (3.3) | 7–19 | |
| WAIS-III Digit Symbol (SS) | 10.9 (2.2) | 6–15 | 10.4 (2.9) | 5–16 | |
| WAIS-III Arithmetic (SS) | 11.5 (2.5) | 6–15 | 11.1 (2.3) | 5–14 | |
| WAIS-III Digit Span Backward (raw) | (6.92.1) | 3–11 | 7.1 (2.2) | 4–14 | |
| PASAT-2 (raw) | 36.0 (9.1) | 16–53 | 34.9 (10.8) | 15–60 | |
| Verbal Story Memoryd | 0.04 (0.94) | −1.59–1.72 | −0.07 (0.93) | −2.20–1.52 | .94 |
| WMS-III Logical Memory 1st Recall (raw) | 26.6 (6.3) | 16–38 | 25.3 (6.1) | 14–36 | |
| Logical Memory I–Total (SS) | 9.7 (2.9) | 5–15 | 9.4 (2.6) | 4–14 | |
| Logical Memory II–Total (SS) | 10.5 (2.7) | 5–16 | 10.5 (2.7) | 5–16 | |
| Logical Memory Recognition (raw) | 26.5 (2.7) | 19–30 | 26.1 (3.0) | 17–30 | |
| Verbal List Learning | 0.08 (1.00) | −1.81–1.63 | −0.12 (0.82) | −2.22–1.54 | .94 |
| CVLT-II Total Recall (T score) | 53.8 (9.4) | 35–69 | 51.7 (8.5) | 28–66 | |
| CVLT-II Short Delay Free Recall(Z score) | 0.09 (1.1) | −2.0–2.0 | 0.12 (0.8) | −2.0–2.0 | |
| CVLT-II Long Delay Free Recall (Z score) | 0.07 (1.2) | −2.5–1.5 | −0.13 (1.0) | −2.5–1.5 | |
| CVLT-II Recognition Discrim. (Z score) | −0.12 (0.9) | −2.0–1.0 | 0.15 (0.9) | −2.5–1.0 | |
| Verbal Accuracy | 0.05 (0.84) | −3.05–0.91 | −0.04 (0.66) | −1.55–0.91 | .61 |
| D-KEFS Verbal Fluency Rep. Errors (raw) | 0.6 (1.2) | 0–5 | 0.7 (0.8) | 0–2 | |
| CVLT-II Total Repetitions (Z score) | 0.34 (1.0) | −1.0–4.0 | 0.23 (1.3) | −1.0–5.0 | |
| CVLT-II Total Intrusions (Z score) | 0.0 (0.9) | −1.0–2.5 | 0.29 (0.9) | −1.0–2.5 | |
| Sequencing Abilityd | 0.31 (0.73) | −2.02–1.18 | −0.31 (0.87) | −2.49–0.86 | .60 |
| D-KEFS Trails Switching (SS)e | 11.1 (1.8) | 6–14 | 9.9 (2.1) | 4–13 | |
| D-KEFS Trails Total Errors (SS)e | 11.4 (1.3) | 6–12 | 10.3 (1.3) | 7–12 | |
| Planning & Problem Solving | −0.15 (0.57) | −1.04–1.19 | 0.20 (0.79) | −1.55–2.56 | .65 |
| D-KEFS Towers Achievement (SS) | 9.6 (1.9) | 6–15 | 10.8 (2.8) | 6–19 | |
| D-KEFS Towers Item #9 Score (raw) | 0.9 (.7) | 0–3 | 1.2 (.9) | 0–4 | |
| D-KEFS Towers Accuracy (SS) | 8.1 (2.4) | 2–12 | 9.4 (2.2) | 6–14 | |
Note. SS = Scaled Score; CVLT-II = California Verbal Learning Test-Second Edition; D-KEFS = Delis–Kaplan Executive Function System; PASAT = Paced Auditory Serial Addition Test; WASI = Wechsler Abbreviated Scale of Intelligence; WAIS-III = Wechsler Adult Intelligence Scale-Third Edition; WMS-III = Wechsler Memory Scale-Third Edition, LM = Logical Memory subtest.
All composite variables used converted Z scores based on control and marijuana-user participants (N = 65).
Age-adjusted norm-based scaled scores and Z scores (when available) and raw scores for individual neuropsychological measures are provided for descriptive purposes only; sample-based Z scores were used in statistical analysis.
Composite variable reliability analysis used Cronbach’s standardized α.
Group status significantly (p < .05) predicted composite score after controlling for gender and lifetime alcohol use. Lifetime marijuana use significantly (p < .05) predicted composite score after controlling for lifetime alcohol use.
Follow-up analysis; group status predicted individual subtest (α = .05/number of subtests within a composite score).