Objective:

To examine the independent and interactive contributions of impulsivity and emotion dysregulation in adolescents with comorbid bipolar disorder (BD) and substance use disorder (SUD), highlighting the significance of these factors for clinical outcomes.

Key Findings:

• Significant BD × SUD interactions for emotion regulation (F(1,120) = 35.89, p < .001) and impulsivity (F(1,120) = 9.51, p = .002).
• The BD+SUD group had the highest scores on both measures, exceeding the SUD-only group by 38.90 points on emotion dysregulation and 26.72 points on impulsivity.
• In the substance-using subsample, impulsivity was the strongest predictor of substance use severity (B = 0.61, p < .001; R2 = .48).
• The BD+SUD group displayed earlier illness onset, mixed-feature predominance, greater polydrug use, and exclusive high-lethality suicide attempts.
• Low income was the strongest exploratory predictor of clinical group membership.

Interpretation:

The findings support an additive comorbidity model where BD and SUD jointly amplify impulsivity and emotion dysregulation, emphasizing the need for integrated, impulsivity-focused interventions in adolescents with dual diagnoses.

Limitations:

• Cross-sectional design does not permit causal inference and may introduce biases.
• Sample size may limit generalizability.

Conclusion:

The study highlights the urgent need for integrated, impulsivity-focused interventions in adolescents with dual diagnoses to improve clinical outcomes.