The percent of subjects who took at least one dose of SPN-812 (Safety Population; N) and who reported at least one Adverse Event (n). The percent is calculated by dividing "the number of subjects who reported at least one Adverse Event (n)" by "the number of subjects in the Safety Population (N)" and multiplying the product by 100. The higher the percentage, the higher the incidence in the Safety Population

The Primary Endpoint was the change from baseline in the Adult ADHD Investigator Symptom Rating Scale (AISRS) Total score at Week 6. The AISRS is an ADHD-specific rating scale designed and validated to assess current ADHD symptomatology in adults. The AISRS consists of 18 items that directly correspond to the 18 symptoms of ADHD per the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5). The scale is subdivided into two subscales: Inattention (9 items) and Hyperactivity/Impulsivity (9 items). The clinician/investigator rates the subject on each item using a 4-point scale, where 0=none, 1=mild, 2=moderate, and 3=severe. A Total score is calculated by summating the ratings of all 18 items (range: 0-54; the higher the score, the more severe the ADHD symptoms). A lower change from baseline AISRS Total score (\<0) represents a better outcome.

The Primary Endpoint was the change from baseline in the Attention-Deficit/Hyperactivity Disorder Rating Scale, 5th Edition (ADHD-RS-5) Total score at Week 7 (End of Study). The ADHD-RS-5 is an ADHD-specific rating scale designed and validated to assess current ADHD symptomatology. The scale consists of 18 items that directly correspond to the 18 Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) symptoms of ADHD. Each item is rated on a 4-point Likert-type scale from 0 (never or rarely) to 3 (very often). A Total score is calculated by adding the responses of all 18 items (range: 0-54; the higher the score, the more severe the ADHD symptoms). Lower change from baseline scores (\<0) represent a better outcome.

The Primary Endpoint was the change from baseline in the Attention-Deficit/Hyperactivity Disorder Rating Scale, 5th Edition (ADHD-RS-5) Total score at Week 6 (End of Study). The ADHD-RS-5 is an ADHD-specific rating scale designed and validated to assess current ADHD symptomatology. The scale consists of 18 items that directly correspond to the 18 Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) symptoms of ADHD. Each item is rated on a 4-point Likert-type scale from 0 (never or rarely) to 3 (very often). A Total score is calculated by adding the responses of all 18 items (range: 0-54; the higher the score, the more severe the ADHD symptoms). Lower change from baseline scores (\<0) represent a better outcome.

The Primary Endpoint was the change from baseline in Attention-Deficit/Hyperactivity Disorder Rating Scale, 4th Edition (ADHD-RS-IV) Total score at Week 8 (End of Study). The ADHD-RS-IV is an ADHD-specific rating scale designed and validated to assess current ADHD symptomatology. The scale consists of 18 items that directly correspond to the 18 Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV) symptoms of ADHD. Each item is rated on a 4-point Likert-type scale from 0 (never or rarely) to 3 (very often). A Total score is calculated by adding the responses of all 18 items (range: 0-54; the higher the score, the more severe the ADHD symptoms). Lower change from baseline scores (\<0) represent a better outcome.