Inattentiveness and impulsivity in healthy adults and individuals with attention deficit hyperactivity disorder (ADHD) diminish these individuals' quality of life. Cortical hypometabolism has been hypothesized to contribute to inattentiveness in ADHD. Transcranial photobiomodulation (tPBM) is a safe and non-invasive modality for activation of the prefrontal cortex. tPBM in healthy adults has been shown to augment brain oxygenation, cognition, and mood. The cognition-enhancing effect of tPBM on sustained attention in adults with ADHD remains unstudied. The investigators will evaluate whether tPBM administration to adults with and without ADHD can improve their attention. Each participant will be screened for eighteen criteria based on the Diagnostic and Statistical Manual (DSM-IV, text revised), using the validated instrument Adult ADHD Self-Report Scale (ASRS-v1.1). Blinded participants will be randomized into (I) Active-tPBM or (II) Sham-tPBM groups. After undergoing an 8-minute administration of Sham or 1064 nm tPBM to the lateral and medial right prefrontal cortex, each participant will complete a 14-minute, computer-based Conner's continuous performance task-3 (CPT-3). The investigators will examine whether adults with and without ADHD who receive Active-tPBM improve in measures of inattention, impulsivity, sustained attention, or vigilance compared to the Sham-tPBM group. Cognitive assessments of attention like the CPT-3 may evaluate the efficacy of tPBM to increase cortical metabolism in healthy adults and individuals with conditions like ADHD. The investigators anticipate their investigation will be a starting point for more sophisticated studies that focus on the implications of tPBM on cognition.

Inclusion Criteria:

• 18 years of age or older

Exclusion Criteria:

• None

What data will be shared? Individual participant data that underlie the results reported in this study, after deidentification (text, tables, figures, and appendices).

A data dictionary, including a description of the variables and types of data, collected for each individual, will be provided. This data will include anonymized individual participant demographic information and all outcome variables (continuous performance task, spectroscopy data).

Beginning 9 months and ending 36 months following article publication.

The raw data will be made available by the researchers upon reasonable request by any qualified doctoral researcher (PhD, MD). They will be granted access by contacting the corresponding author/principal investigator (F. Gonzalez-Lima, gonzalezlima@utexas.edu).

It will be made available to qualified researchers whose proposed use of the data has been approved by an independent review committee (Institutional Review Board) identified for the purpose of individual participant data meta-analysis.

Proposals may be submitted up to 36 months following article publication. After 36 months, the data will be available in our University's shared network drive, but without investigator support other than deposited metadata.