ADHD vs Borderline: How to Diagnose and Treat

Emotional dysregulation looks identical in both disorders

STUDY: Christen A et al, Frontiers in Psychiatry 2026

STUDY TYPE: Cross-sectional case-control study

FUNDING: Independent

Background

ADHD and borderline personality disorder share overlapping symptoms:

• Emotional dysregulation
• Impulsivity
• Unsteady self-concept

This study looks at what separates them.

The Study

• 80 adults with ADHD, 55 with borderline personality disorder, and 55 healthy controls in Switzerland.
• All completed self-report scales measuring ADHD symptoms (CAARS), borderline symptoms (BSL-23), and emotional impulsivity (EIS).
• Cross-sectional comparison, no follow-up.

ADHD patients scored higher on inattention, hyperactivity, and impulsivity (effect sizes around 0.3). Borderline patients scored higher on self-concept problems (effect size 0.32) and, more dramatically, on suicidal behavior (a large effect).

Both disorders had similar elevations of emotional impulsivity and lability (rapid emotional swings).

Interestingly, borderline patients also scored higher than controls on inattention and hyperactivity, even though those aren’t core borderline symptoms.

Limitations

Gender was imbalanced: The borderline group was 96% female while the ADHD group was 63% male. The scales used were built to assess ADHD, not borderline pathology, which may have shortchanged the borderline group’s presentation. Most participants were on psychiatric medications, but type not reported.

Practice Implications

1. Emotional dysregulation doesn’t differentiate ADHD from Borderline, but inattention, hyperactivity, and possibly impulsivity do.
2. Caution with stimulants in borderline personality disorder. While methylpheniate improved executive function in a small randomized trial of borderline with ADHD, early studies on amphetamines were abandoned in borderline because they triggered aggression and paranoia at a high rate (Schulz, 1985; Schulz 1988).
3. Clonidine is an ADHD treatment with anti-aggressive properties. It reduces self-harm and hyperarousal in borderline.
4. Omega-3, DBT therapy, and mindfulness also have evidence in both disorders.
5. Another type of “emotional dysregulation” is cyclothymia. This temperament is common in ADHD, borderline, and bipolar disorder. Screen for it with the TEMPS-A, and learn more about this complicated overlap in our Carlat Podcast.