Females who suffered early concussion may be more likely to drink alcohol in later life.
Alcohol is already linked to traumatic brain injuries, since an estimated 33-50% of concussion patients are intoxicated at the time of the injury. The most common cause of nonmilitary brain injuries is a car accident.
Other groups increasingly prone to head injury are elderly people and young women, particularly those involved in athletics.
Scientists from Ohio State University, led by Zachary Weil, assistant professor of neuroscience, carried out experiments on mice to see what effect a concussive head injury would have on their attraction to alcohol, and whether this could be reversed.
In the experiment, mice received a concussive head injury aged 21 days - the equivalent of 6-12 years in humans.
Female mice more likely to drink alcohol after concussion
Later, they were allowed to choose between two bottles: one containing water and the other containing escalating doses of ethanol diluted in water. The amount was adjusted over time because mice do not like the taste.
Female adult mice that had been injured at 21 days of age drank significantly more ethanol than those that had not. The juvenile head injury had no effect on drinking in male mice.
Physiological tests suggested the injury did not affect how the animals processed alcohol. This led researchers to believe that the young, injured, female mice linked the alcohol with a reward.
To investigate this further, mice were placed in a box with visibly different patterns covering separate sections of the floor. Over 10 days, researchers injected them with alcohol in specific sections of the box and with saline in other sections.
The mice were allowed to walk back and forth between boxes. Those that liked alcohol would spend more time on the side associated with alcohol. Females that had been injured spent about 65% of their time in the box linked to alcohol - significantly more than the uninjured mice.
The researchers say this proved that there is something about the way reward and pleasure is processed in these animals with regard to alcohol.
Follow-up care can reverse the tendency
Finally, they hypothesized that with sustained follow-up care after a human brain injury, the attraction to alcohol could be reversed.
- TBI contributes to about 30% of all traumatic deaths in the US
- 138 people die every day in the US from injuries involving TBI
- In 2009, nearly half a million children visited the emergency department for sports-related TBI/concussion.
Weil and colleagues set up an enriched environment to mimic follow-up care for injured patients. They put recently injured mice in bigger cages with running wheels, toys and tunnels, providing a new experience every week for 6 weeks. Control injured animals lived in standard housing conditions.
When the mice were tested for alcohol intake, the enriched environment had completely blocked the females' increase in drinking. The enriched environment also reduced axon damage in their brains by about 40%.
Overall, it appears that females with a mild closed-head brain injury are more likely to misuse alcohol later in life and to associate drinking with reward and pleasure - an effect that was not seen in males.
On the other hand, the effect is reversible with an enriched environment. Apart from preventing increased drinking, the environmental enrichment also reduced degeneration of axons - the long, slender extensions of the nerve cell body.
"There are ways to intervene, but they're expensive in terms of effort and money. It requires sustained treatment and rehabilitation and educational support. The best therapy for a childhood brain injury is everybody getting great medical care and rehabilitation, regardless of socioeconomic status.
People with juvenile head injuries are already at risk for memory problems, difficulty concentrating, poor learning and reduced impulse control. If we can prevent alcohol misuse, chances for a good life are much better."
Weil plans to follow up by studying whether hormones cause the difference in alcoholism risk between males and females with juvenile head injuries, and if so, at which stage of life they would be most active.
Earlier this year, Medical News Today reported that heading a ball in soccer is a common cause for concussion injury.