NYC shooting suspect claimed he had CTE: What to know about the disease

• The suspect, identified by police as 27-year-old Shane Devon Tamura, died Monday from what police said was a self-inflicted gunshot wound.
• The NYPD said Tuesday that Tamura had a note on his body that suggested he blamed the NFL for his mental illness and claimed that he had CTE, though a diagnosis has not been confirmed.
• Tamura played high school football in California, former teammates confirmed to NBC News.

What is CTE?

CTE is a brain disease that is likely caused by repeated head injuries, according to Mayo Clinic.

• Football players have been most commonly linked to CTE, but the disease has also shown up in athletes from other contact sports — such as soccer and hockey — as well as in members of the military who experienced combat.
• The only way to definitively diagnose CTE is after death during an autopsy of the brain.
• Studies have shown that younger individuals with CTE are more likely to present with mood and behavior symptoms, while older individuals commonly exhibit cognitive impairment and executive dysfunction.

What does CTE have to do with football?

The number of years playing football can be associated with CTE diagnoses, the NIH said in a study.

• A separate study conducted by Boston University found that for every 2.6 years an athlete played football, the likelihood of developing CTE doubled.
• Multiple studies have shown that the number of concussions sustained during a contact sport doesn't determine if a person will develop CTE, but rather the number of hits an athlete takes during their playing career.

By the numbers: A study by Mass General Brigham of nearly 2,000 former NFL players shows that about one-third believe they have chronic traumatic encephalopathy.

• Those who believed they had CTE were still twice as likely to report frequent thoughts of suicide or self-harm, even if they reported similar levels of depression.
• Another study found that CTE was found in 99% of the deceased NFL players' brains that were donated to scientific research.

Yes, but: While CTE in football players is a big concern, the attention on one specific disease could be overshadowing the need to treat other conditions, such as pain management and cardiovascular disease.

Is there treatment for CTE?

Little is known about how CTE progresses.

• CTE also has no cure, and treatment primarily focuses on managing symptoms, according to the National Institute of Health.
• Cognitive improvement can be supported through cognitive rehabilitation therapy, a Mediterranean diet and aerobic exercise, the NIH said.
• Strict adherence to preventive measures and safe practices is the best practice to prevent CTE.

What has the NFL said about CTE?

State of play: For years, the NFL never explicitly linked playing football to CTE or any other long-term health side effects.

• Thousands of former NFL players sued the league for long-term brain injury, resulting in a landmark settlement in 2015 in which NFL awarded more than $1.2 billion to more than 1,600 athletes, though some former players said their compensation and medical care compensation claims are getting denied.
• Some of former NFL players who were diagnosed with CTE include John Mackey, Ollie Matson, Ken Stabler, and Aaron Hernandez.
• In 2016, the NFL's top health and safety officer acknowledged to Congress the link between football-related head trauma and CTE.

What they're doing: Currently, the NFL is working with its player association to invest in brain injury research, as well as increasing the standard for helmet protection.

• More than 200 National Football League players have been using shock-absorbing helmets aimed at reducing concussions.
• The NFL also conducts annual laboratory testing performed by biomechanical experts to evaluate which helmets best reduce head impact severity, according to its website.