Mental Health and Substance Use-Related Hospitalizations Among Women of Reproductive Age in Illinois and Wisconsin.

Introduction: Mental health and substance use are growing public health concerns, but established surveillance methods do not measure the burden of these conditions among women of reproductive age. We developed a standardized indicator from administrative data to identify inpatient hospitalizations related to mental health or substance use (MHSU) among women of reproductive age, as well as co-occurrence of mental health and substance use conditions among those hospitalizations. Materials and Methods: We used inpatient hospital discharge data from 2012-2014 for women aged 15-44 residing in Illinois and Wisconsin. We identified MHSU-related hospitalizations through the principal International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) diagnosis and first-listed ICD-9-CM external cause of injury code (E code). We classified hospitalizations as related to 1 of 3 mutually exclusive categories: a mental disorder, a substance use disorder, or an acute MHSU-related event. We defined co-occurrence as the presence of both mental health and substance use codes in any available diagnosis or E-code field. Results: Of 1 173 758 hospitalizations of women of reproductive age, 150 318 (12.8%) were related to a mental disorder, a substance use disorder, or an acute MHSU-related event, for a rate of 135.6 hospitalizations per 10 000 women. Of MHSU-related hospitalizations, 115 163 (76.6%) were for a principal mental disorder, 22 466 (14.9%) were for a principal substance use disorder, and 12 709 (8.5%) were for an acute MHSU-related event; 42.4% had co-occurring mental health codes and substance use codes on the discharge record. Practice Implications: MHSU-related disorders and events are common causes of hospitalization for women of reproductive age, and nearly half of these hospitalizations involved co-occurring mental health and substance use diagnoses or events. This new indicator may improve public health surveillance by establishing a systematic and comprehensive method to measure the burden of MHSU-related hospitalizations among women of reproductive age.