The Connecticut medical examiner has asked scientists to analyze the DNA of Adam Lanza, the 20-year-old who killed 27 people, including his mother, two classrooms full of small children and teachers, before killing himself on Dec. 14. 

Investigators hope that studying Lanza's DNA for mutations or other abnormalities may shed some light on the tragedy. Connecticut's chief medical examiner, Dr. H. Wayne Carver II, called the University of Connecticut a few days before Christmas asking for help from the UConn Health Center’s Department of Genetics and Developmental Biology, said UConn spokesman Tom Breen.

“They have agreed to offer any assistance they can to help the chief medical examiner in his investigation,” Breen said. Of Carver, Breen said, “He wanted help in conducting tests relating to genetics involving the shooter in the Newtown massacre.”

Breen said did not know what specific tests would be conducted. He said UConn was happy to help.

“This is such a terrible thing,” Breen said. “Everybody in the state has been affected by this.”

Will a DNA analysis help explain Lanza's rampage? 

The study of Lanza's DNA would be for research purposes, not to find a diganosis for his acts, says Arthur Caplan, Ph.D, NBC News contributor and head of Division of Bioethics at New York University Langone Medical Center in New York City. While there has been prior research on genetic mutations and violent behavior, looking at someone’s genes "is like hunting in a DNA haystack," Caplan says.

"We don’t have a database that says there’s a correlation between genes and propenstity to violence or crime or propensity to mental illness," he says.  "A particular DNA message may indicate a propensity to behavior, but at best you might find associations to greater risk. You won’t find a gene that says I’m going to be a mass murderer or a terrorist or an assassin."

James Fallon, a neuroscientist at the University of California, Irvine, who studies serial killers and other violent criminals, argues it will be fruitless to try to pin Lanza’s acts on his genes alone. Genetic data only paints part of the picture, he's found.

"The genes by themselves don’t tell you. If you just have a PET scan or MRI you can’t tell," Fallon said last week. "The psych report alone won't tell you. You put those things together you really get a lot of information." And some of what's been found by Fallon and other researchers provides some surprising insights.

Take for instance the “warrior gene”, the monoamine oxidase-A, or MAOA, gene that, has received widespread media attention, said Fallon.

“People know about the warrior gene and that it is associated with psychopaths and with killing,” Fallon said in a telephone interview.

Only a handful of diseases, such as cystic fibrosis, cause symptoms based on a single mutated gene. Most require thousands of changes and interactions. “So the idea that you have the warrior gene, therefore you are a warrior, it doesn’t hack it,” Fallon says.

It takes something more than just a genetic predisposition to make someone violent.

Fallon says there is no scientifically acceptable body of work on the genetics of violent behavior. "I don’t know of a case where even one killer has been studied genetically to an appropriate level, " Fallon said.

Likewise, brain studies have shed some light but can’t explain or predict the most extreme behaviors, said Dr. Martin Teicher, director of the Developmental Biopsychiatry Research Program at Harvard Medical School and McLean Hospital in Massachusetts.

“I don’t think we have the answer from neuroscience,” Teicher said. “Given the millions of people there are, the tiny handful of people who did these things are quite rare … We are drawing generalities from people who have had bad experiences, and who are maybe more prone to get into a fight, but they never would do anything like this.”

There is something that many violent people do have in common, however. Research done by Teicher, Fallon and others shows that violent criminals are, in fact, excessively anxious and fearful.

“Individuals at risk for violence often suffer from tremendous anxiety,” Teicher said. “It’s one of the most striking things I have noticed.” He’s treated high school students expelled or suspended for violence, but when they are in his office, they are anything but threatening.

“These are the frightening children in high school, yet they are essentially sitting in their mother’s laps,” Teicher said. “They were ridden with anxiety.”

And in some cases, this is combined with an inability to “read” other people. Teicher’s found this in some patients.

“We found differences in the (brain) cortex of violence-exposed individuals that play a role in social perception,” Teicher said. “These are regions involved in being able to infer what other people are thinking.” Brain scans show that the blood isn’t flowing normally in those brain regions. “They may be prone to misattribute thoughts and feelings,” Teicher says. 

Such deficiencies can be immensely stressful to a young man or teenager, Fallon says. “He looks at people and doesn’t understand what they are feeling,” he said. 

On top of this, Teicher has seen differences in parts of the brain’s frontal cortex that are involved in impulse control. “Misreading people and having difficulty controlling impulses may foster inappropriate actions,” Teicher says.

And while schizophrenia or bipolar disease do not usually lead to violent behavior, they can contribute to dangerous acts if patients are also racked with anxiety and not getting any sort of treatment.

“The late teens, early 20s, are when people have these psychotic breaks," Fallon said.

Most young people with these developing psychiatric conditions may feel anxious or threatened, but they don’t actually act on their feelings in part because they are unable to, Fallon said. Studies show the adolescent brain lacks the connections to initiate certain actions.

The brain is still growing, making new connections and cutting unneeded circuits, until the early 20s, Fallon said. The prefrontal cortex, involved in “executive function” or decision-making, is the last part of the brain to mature.

In an anxious young man, unable to understand people around him, perhaps ascribing all sorts of mistaken intentions to others, this could come to a climax, said Fallon, who studies how message-carrying chemicals such as dopamine and norepinephrine act in the brain. 

The young man's brain is still growing and changing until, finally, the prefrontal cortex matures. The amygdala, the part of the brain responsible for fear responses on the most basic level, is at the same time being flooded with corticotropin-releasing hormone, which is involved in the brain's stress response. 

“He is finally able to take action,” Fallon says. “Now the moment has come for him to carry out the ultimate act. If you turn it around like that, it makes a lot of logical sense."

Lisa Flam contributed to this story. 

Related stories:

• Asperger's not to blame for killer's actions
• After massacre, parents even more divided on guns
• Nancy Lanza buried

By many accounts, Adam Lanza didn’t fit in. Family friends and neighbors describe a young man who went far beyond shy in avoiding people, who had few or no friends, and who dressed unlike most of peers, buttoning up his shirt to the top and carrying a briefcase to high school instead of a backpack.

Several people, including Ellen Adriani, a friend of his mother, Nancy Lanza, have now said he had Asperger’s, a type of autism, although there’s been no official medical confirmation of this.

“Nancy was always concerned about Adam because of his Asperger’s and the typical behavior that goes along with that,” Adriani told NBC News.

If Adam Lanza did have Asperger’s syndrome or another form of autism, he committed the unfathomable murders of 20 children, six school staff and his own mother despite the condition, not because of it, experts agree.

The kind of carefully planned, violent attack like the killings in Newtown, Conn., on Friday would be out of character for someone with Asperger’s, said autism expert Travis Thompson, Ph.D., of the Special Education Program at the University of Minnesota.

“I have known a lot of people with Asperger’s and I have never known one who is violent. They are very anxious,” Thompson said. “They have a lot of problems with anxiety and they have problems with relationships with other people too but that doesn’t translate into violence. When they are little kids, they have tantrums because they don’t know what to do and they feel adults don’t understand them. When they become older they develop mechanisms and since they are usually very verbal they can ask questions.”

Parents of kids with Asperger’s worry about the discrimination that could come from all the speculation.

“I think a lot of parents who are dealing with this already are awash with anxiety and uncertainty, and when someone sits in front of the camera and says people like my son are dangerous because of an association with a condition, it’s scary,” says Ron Fournier, editorial director at National Journal, who has written several recent high-profile commentaries about his son with Asperger’s.

Julie Steck, a child and pediatric psychologist in private practice in Indianapolis, said people with a developmental disorder like autism are more likely to have a range of other physical and mental disorders.

That’s in part because of the genetics, in part because of the stress of coping with the disorder itself, she said.

Family friend Adriani said Adam Lanza also had an unusual condition where he didn’t feel physical pain. “If he were to cut himself or even if he fell down or if he injured himself he wouldn’t necessarily know how severe it was because usually the pain is, oh something’s wrong.  So if he cut himself he wouldn’t even necessarily know it,” she said.

Richard Novia, who was Lanza’s tech club adviser at Newtown High School, backed that detail in an interview with the Associated Press. "If that boy would've burned himself, he would not have known it or felt it physically," Novia said.

It's not clear to experts if that is tied to Asperger's. "Individuals with Asperger’s often have poorly modulated responses to pain—they may over-react to something which seems minor to others but totally block out or not respond to something we would see as painful," says Steck. "However, I am not familiar with there being a correlation with not feeling or being able to respond to pain at all."

Russell Hanoman, another friend of Nancy Lanza, described Adam as being obviously uncomfortable around other people.

“I remember when I first met him, he deliberately stood maybe six feet away from me and took three exaggerated steps toward me, stuck out his hand, shook it, put it back, and three exaggerated steps back,” Hanoman told NBC News.

Thompson also said it is unlikely a person with Asperger’s would have plotted something like Friday’s shootings over a long period of time without telling someone about it.

“I am not saying a person with Asperger’s would not do something like this,” he said. “It is possible a person with Asperger’s could have done something like this but so might someone who was depressed or someone with schizophrenia.” Or someone with no diagnosed mental illness at all.

Descriptions of Lanza’s painfully awkward ways have fueled speculation that he might have been lashing out after a childhood of having been bullied.

But there’s no evidence that Lanza was bullied, and Thompson doesn’t see the connection between any possible bullying and the murders. “Why would he go in and kill a bunch of little children?” Thompson asked.

One thing psychologists do agree on – mental health is still not adequately diagnosed or treated in the United States, and especially not among young people.“We need to destigmatize it so that people seek treatment for their children and for themselves. I think obviously that funding is a huge issue,” said Steck, the Indianapolis child and pediatric psychologist. “It is very under recognized and under financed and many of the programs out there are not delivered in a very effective manner.”

Connecticut Gov. Dan Malloy agrees.

“Mental illness has long been relegated to a different discussion, as has physical health,” Malloy said at a Hartford, Conn., news conference Monday about the shootings. “It is not a distinction that I think serves our country. We need to begin in earnest the process of removing that distinction.”

NBC News’ Michael Isikoff contributed to this report.

In his speech at the memorial service for the Newtown victims, President Barack Obama included mental health in calling for a national response to the massacre, a conversation that so far has focused on gun control. "I will use whatever power this office holds to engage my fellow citizens -- from law enforcement to mental health professionals to parents and educators -- in an effort aimed at preventing more tragedies like this," the president said.

On Monday, White House spokesman Jay Carney pointed to the federal health reform law as evidence that the administration has already started to tackle the issue. Mental health issues are "clearly a factor that needs to be addressed in some of these cases of horrific violence," Carney said. "Obamacare, if you will, has ensured that mental health services are a part of the services" provided under the health law.

Insurance coverage for mental health treatment has long been spotty. More than a quarter of U.S. adults have a diagnosable mental health problem in any given year, but fewer than half receive treatment. While the Affordable Care Act, along with the Mental Health Parity Act of 2008, go a long way toward assuring coverage for most Americans, some gaps persist. There are questions, for example, about just what counts as equivalent treatment under the parity law, and whether it's being fully enforced. 

Here are some answers to frequently asked questions about mental health coverage:

Didn't the Mental Health Parity Act already guarantee coverage for Americans with insurance?

The Mental Health Parity and Addiction Equity Act, signed into law in 2008, made a big dent in the problem of mental health coverage.

Under that law, employers with more than 50 workers that include mental health services in their insurance plans were barred from covering them at a lower level than other medical conditions. That means that the plans could not provide fewer inpatient hospital days or require higher out-of-pocket costs, more cost sharing or separate deductibles for mental health conditions.

An estimated 140 million Americans were expected to benefit from the changes. But Paul Samuels, director and president of the Legal Action Center, says that some people still aren't receiving equal coverage, and the law is not always enforced. "That's a problem we're really concerned about," he says.

And while the law guaranteed parity for employees of companies that chose to offer mental health coverage, the law didn't require employers to offer such coverage. Even so, in 2012, 85 percent of employers offered some form of mental health benefits, according to the Society for Human Resource Management.

Mental health coverage under small business and individual market plans was not included in the Parity Act. In short, whether you have mental health coverage in an employer-sponsored insurance plan depends on where you work.

What if I don't have mental health coverage in my employer’s insurance plan? Will the ACA change that?

Employers with 50 or more workers can continue to not offer the benefits. But small group and individual plans will be required to offer the coverage in 2014 through online exchanges created under the law.

I'm planning to buy an insurance plan through one of the new exchanges. What kind of mental health coverage will I have?

All plans sold in the exchanges will be required to provide coverage for mental health and substance abuse as one of 10 essential benefit categories. That coverage must also comply with the parity laws already required for large employers. The exchanges will be open to individuals and small businesses.

The same rules will apply to small group and individual plans purchased outside of the exchange.

This means that beginning in 2014, if you, or your small employer, are purchasing any new insurance plan, coverage will include mental health benefits on par with any other medical condition. It’s not clear what exactly will be covered – for example, group home and residential treatment outside of a hospital.

I'll be covered under the Medicaid expansion authorized by the law. What kind of mental health coverage will I get?

If you earn less than 138 percent of the federal poverty level (about $32,809 for a family of four), you may be newly eligible for Medicaid coverage in 2014. Like people who purchase coverage through the exchange, new Medicaid beneficiaries will receive mental health benefits on par with other medical or surgical needs.

That coverage is less robust than the current traditional Medicaid coverage offered by states, says Jennifer Mathis, deputy legal director at the Bazelon Center for Mental Health Law. That's because most states offer mental health benefits for Medicaid recipients that are more generous than the coverage offered by commercial insurance plans. But the new Medicaid benefits will be modeled on and measured against private insurance purchased by small businesses now.

Mathis says, however, that it will likely be difficult for states to maintain two parallel Medicaid programs, one for current beneficiaries and a second for the newly eligible. She hopes that most will choose to offer all Medicaid recipients the more robust benefits instead.

What else in the ACA may improve mental health treatment?

The ACA has several other provisions that will affect mental health coverage and treatment.

The Prevention and Public Health Fund created by the law, for example, includes $35 million to integrate primary care and mental health care, $10 million to train and recruit mental health professionals, and an additional $53 million in mental health screening, surveillance and suicide prevention funds.

The ACA also requires that plans offer depression screening for adults without a copayment, co-insurance or a deductible.

What problems might arise?

While the ACA "provides enormous potential and opportunity to make sure than many millions more Americans obtain the services they need," says Samuels, "that will only happen if the implementation of those reforms is effective." Samuels worries that the rules from HHS will not be clear or strong enough to make the parity laws meaningful. He also worries about getting everyone who is eligible for coverage enrolled, particularly those with severe mental health disorders who be may homeless or living on the fringes of society.

In addition, governors in several Republican states have said that they will not expand Medicaid, leeway they were given by the Supreme Court's health law decision in June. That could leave many Americans without any form of insurance coverage, including mental health benefits.

Access to treatment will likely also remain a serious stumbling block. States have cut $4.35 billion in public mental health spending from 2009  to 2012, a trend that is likely to continue over the next several years, according to the National Association of State Mental Health Program Directors. At the same time, the system has seen nearly a 10 percent increase in usage.

As many as 30 million people are expected to gain insurance coverage beginning in 2014. Of those, the U.S. Substance Abuse and Mental Health Services Administration estimates that 6 to 10 million will have untreated mental illnesses or addiction, adding additional demands to a system that is already overwhelmed. Patients may experience long wait times to see a psychiatrist, for example, and may require additional investments to expand the mental health workforce.

"I think there will be initial period where you may see folks with mental health coverage waiting longer than they'd like to get care," says Joel Miller, senior director of policy and health care reform at the state mental health program directors group.

Kaiser Health News is an editorially independent program of the Henry J. Kaiser Family Foundation, a nonprofit, nonpartisan health policy research and communication organization not affiliated with Kaiser Permanente.

NEWTOWN, Conn. -- It's not a conversation parents expect they'll have with their kids: But Shari and Andrew Paley were doing just that, talking with their identical twins, Ben and Ethan, about the shooting at their school that left 20 of their fellow students dead.

Ben and Ethan, a pair of articulate and observant nine years olds, had many questions and much commentary for their parents about the tragedy at Sandy Hook Elementary School, where they are in the fourth grade. 

“We know lots of things that we shouldn't know,” Ethan said Saturday while talking with a reporter and munching on a green-frosted, white-sprinkled, crème donut.

John Makely / NBC News

Shari and Andrew Paley, with their children Jacob, 3, Ethan, 9 in green jacket, and Ben, 9, in black jacket.

His mother said earlier he had noted that he has lived through a tornado, two hurricanes and now this.

“Remember what we talked about last night, that sometimes when something really bad happens you learn to appreciate what you have,” she told the boys. “You don't take any(thing) for granted.”

Ethan and Ben were at school Friday morning when the alleged shooter, Adam Lanza, opened fire, taking the lives of their fellow students and six administrators, including their principal.

Story: Talking to kids about school shooting: Be calm

Ethan was in the gym for an ice skating exercise, when they heard a loud bang. His teacher taped up the windows to the door and told them to hide in a corner. Ben was in the art room, and they later had to run out to safety.

“We heard the bangs. We heard the policeman say, 'Stop.' We heard the guy scream when he was shot,” Ben said (Lanza took his own life, authorities say).

“It was scary there,” Ben said, later noting that he cried about the shooting. “Ethan did, too,” he added.

There's no guidebook for these kinds of parent-kid conversations,  said Shari, 39, and a speech pathologist.

“I'm just letting them talk. They actually have a lot of questions and I'm trying to answer them the best that I can,” she said. “I'm just going with it.”

Story: Slain hero teacher: 'She loved those students more than anything'

When asked if they knew everything about what happened, Ben said no, though they were aware that 28 people had died.

“I gave them a little bit of information at a time because I didn't want them to find out from somebody else,” Shari said. “I didn't want them to turn on the TV and hear it. I wanted to be the one that explained it to them.”

She said she didn't hide anything and progressed from telling them that a lot of people got hurt to eventually including teachers and then children in that group. “They've been … pretty in control. ... We're just kind of answering their questions and reassuring them that they're safe. We're following their lead.”

The boys shared some of the different rumors they'd heard: that the gunman had mini-machetes and they speculated about which teacher had been wounded in the foot.

“Well, we don't know that,” their mom said of the latter report. “That's the other problem, is that I don't really know all of the facts. … that's the other reason why I am kind of cautious.”

At a local donut shop, the twins ran into friends from school, happily chatting with them. They also twirled around in swivel sofa chairs in front of a television airing coverage of the investigation and the deaths, with one of the boys saying, “breaking news.”

“The only thing that I mean I'm hurt by is ... by sadness,” Ben said.

When asked if he had any worries about returning to school, Ethan said: “Yes, I do have a fear of going back. I mean what if they struck again when we're back to school?”

“That's not going to happen,” Shari said. “It was one bad guy and they got that bad guy.”

His dad, who picked up the boys from the fire station where they had been evacuated to after the shooting, then told him it was OK to be scared. But he also later noted that he was scared that his son was scared, and lamented the loss of their beloved principal, Dawn Hochsprung, who he knows would have been a steady, compassionate hand for the twins on their return to school.

Shari said she hadn't thought about the boys returning to school, one of the questions that Ben has been asking.

“I'm scared for them, just emotionally, their emotional well-being, feeling comfortable to be at school,” she said. “They spend more time at school than they do at home, it's kind of like their home away from home in a way. So if they don't feel safe at their school home -- it's just really important.”

Story: Portrait of the victims: A twin, talented teachers

Ben has also been asking if he can attend all of the funerals. Shari believes it's his way to say goodbye to the victims.

“I think he's putting it together, like kids died there (at the school) and then how do they move from there and where do they go and what happens to them,” she said.

But she is not sure she wants him to go, saying they'll talk about it but also suggesting he write letters to the families.

“You want to shelter your kids as much as you can,” she said. “I don't know it's a process ... that I'm trying to figure out myself.”