A mild traumatic brain injury (mTBI) induces secondary attention-deficit hyperactivity disorder-like symptomology in young rats

Although attention-deficit hyperactivity disorder (ADHD) is commonly reported after moderate and severe traumatic brain injury (TBI), research is struggling to find a strong link between mild TBI or concussion and ADHD. Epidemiological studies often generate conflicting results which may be related to the difficulty identifying the lingering symptoms of mTBI, the lack of baseline knowledge and the possible exacerbation of pre-existing ADHD symptomology, and/or differential diagnostic criteria for secondary ADHD. The purpose of this study was to determine if a mild TBI/concussion in the juvenile period (postnatal day 30) could induce ADHD-like symptoms in young rodents. Using the Go/No-Go paradigm of the 5-choice serial reaction task, sustained attention, impulsivity, and response inhibition was measured. The open field was also used to measure activity levels at two time points. Animals that experienced an mTBI in the juvenile period exhibited ADHD symptomology, with sex-differences present on one of the tasks. Significant deficits were identified in sustained attention, response inhibition, and impulsivity. Immediately after the mTBI, all rats were hypoactive in the open field, and while male animals exhibited a trend toward hyperactivity in the long-term, females continued to trend toward hypoactivity for the duration of the experiment. These findings provide a unique platform upon which preventative and therapeutic strategies can be implemented and tested in an effort to improve ADHD-like symptoms following mTBI.