Table 1. Sample Characteristics.
| Child 1 | Child 2 | |||||||
|---|---|---|---|---|---|---|---|---|
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| N | Mean | (SD) | N | Mean | (SD) | |||
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| Study Variables | ||||||||
| SDP severity | 173 | 3.95 | 2.05 | 167 | 2.04 | 1.77 | ||
| MAGIC inattentive | 173 | 2.68 | 3.20 | 171 | 2.32 | 3.17 | ||
| MAGIC hyperactive/impulsive | 173 | 1.42 | 2.26 | 171 | 1.82 | 2.45 | ||
| MAGIC Total ADHD | 173 | 4.10 | 4.87 | 171 | 4.14 | 5.11 | ||
| SWAN inattentive | 159 | 2.84 | 2.74 | 156 | 3.28 | 3.06 | ||
| SWAN hyperactive/impulsive | 159 | 1.52 | 2.11 | 156 | 2.63 | 2.91 | ||
| SWAN Total ADHD | 159 | 4.36 | 4.24 | 156 | 5.90 | 5.50 | ||
| Covariates | ||||||||
| Maternal age at birth | 143 | 26.64 | 5.40 | 145 | 29.48 | 5.60 | ||
| Maternal education (in years) at birth | 143 | 13.31 | 2.10 | 145 | 13.59 | 1.90 | ||
| Second-hand smoke exposure by fathers | 171 | 1.84 | 1.44 | 159 | 1.13 | 1.42 | ||
| N | % | N | % | |||||
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| Marital status (percent married) at birth | 143 | 85% | 145 | 85% | ||||
| Food stamp usage at birth | 142 | 7% | 142 | 11% | ||||
| Family Demographics (at assessment) | N | Mean | (SD) | |||||
|
| ||||||||
| Maternal age | 162 | 39.83 | 5.62 | |||||
| Paternal age | 80 | 44.04 | 6.34 | |||||
| Child 1 age | 173 | 12.99 | 1.95 | |||||
| Child 2 age | 170 | 10.19 | 1.80 | |||||
| Child age difference | 170 | 2.79 | 1.54 | |||||
| Maternal | Paternal | |||||||
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| N | % | N | % | |||||
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| Education | ||||||||
| Less than HS | 7 | 4% | 9 | 10% | ||||
| HS | 30 | 18% | 19 | 20% | ||||
| 1-2 years college | 50 | 30% | 14 | 15% | ||||
| 3-4 years college | 46 | 27% | 17 | 18% | ||||
| More than college | 29 | 17% | 21 | 22% | ||||
| Not reported | 7 | 4% | 14 | 15% | ||||
| Mothers' marital status | ||||||||
| Never married | 6 | 4% | ||||||
| Married | 130 | 77% | ||||||
| Separated | 5 | 3% | ||||||
| Divorced | 26 | 15% | ||||||
| Widowed | 2 | 1% | ||||||
Note. MAGIC = Missouri Assessment of Genetics Interview for Children; SWAN = Strengths and Weaknesses of ADHD-Symptoms and Normal-Behavior; SDP = Smoking during pregnancy; ADHD = attention deficit/ hyperactivity disorder symptoms; HS = High school. All ADHD variables are presented in this Table as raw and unstandardized data for descriptive purposes; however, for analyses, they are log-transformed and standardized. N's reflect the sample size with valid data and vary due to random missing data in the birth record.