Children contaminated by their own families their friends even their everyday surroundings. Or sold their brains tell them. But telling CNN. It's -- CD. Obsessive compulsive disorder. -- -- -- -- because I couldn't touching things. Handling can't really touch anything can't do any. Our yearlong journey into the medical mystery has taken a million kids happy normal childhoods. To paralyzing secrets and -- An unprecedented look into the breakthrough science therapy rooms and parents never give up. Yes. Can it all work together the final set them. Plunged into darkness families -- a prime time limited to you. Reporting tonight. David -- Inside this suburban office building in New Jersey -- small yellow room. We're a battle is about to play out right in front of our camera. Yeah fifteen year old Bridget looks like your typical teenager on the outside. -- inside she is -- to break free from unimaginable fear. And on this -- her progress is measured in inches. What do you think we'll -- -- Well come on look at. They're just measuring accounts for -- -- life every inch counts he could lean against the. -- mark armrest to hear our. From her elbow to her hand is good. Morning -- the woman at the other -- of the sofa. He's about to move from her chair to the -- Tell it was an accident -- so close to keep this close before it. -- what they think that they. That woman who has -- Soo terrified. He's -- own mother. Would you believe her -- somehow contaminated. And -- fears that her mother and contaminate her to. -- has been diagnosed with obsessive compulsive disorder for particular attention and irrational fear that her own family is somehow contaminated. And because of that contamination. She can't be -- them. -- estimated five million Americans battle obsessive compulsive disorder and doctors say about a million of them are children. How many of us have heard someone say at some point I have a little OCD but this is far different far more debilitating because for children who have OCD. It never lets go. And have to proved her that I can do that's who he's -- talking about and -- CD as if it were person trying to control her. She's not gonna win this time because she's one too many times that. -- -- assistant trip amend his ideal cooled down. -- -- B state BO CD is still winning Houston and corpus. For bridges it's become an all consuming. -- OC is taking over most of my life in the past six months I haven't been able to hit home. -- any of my belongings parent home I haven't really seen any of my friends. Long before -- -- -- and some beautiful little girl smiling from -- year. Growing up playing with her two older Brothers a star student at school in the gifted program. The proud mother and father at home. -- standout swimmer in the school of fish and water. The first signs that all this didn't crack keen interest in London with -- -- mother Karen says was -- need to be perfect school. Everything had to be untrue or -- she had to know every selling learned. Then all of a sudden she started to notice that her -- had to be in the second plane and she didn't want certain things patch she noticed that you're. The bit of a perfectionist had to do everything perfectly with school work. Surprisingly we're able to stand right next to -- and as we talked to -- Why us and not her own family her doctor says this proves just how -- -- OCD convene. We're just mind is fixated on her own family and the OCD won't let go. Eight. Grade miraculously it was. Be much better so I stopped taking reminiscent stopped going to the therapist and then that's when this came up. -- OCD would come back with a vengeance. This time for fear it morphed into contamination. The contamination. And think about as being something that's dirty radiation or something like that -- grants energy -- -- Allen winning. Her convergence case how do you go from. Being a perfectionist. To someone who can't. Touch her parents can even be in the same homer but it seems so extreme you have to think about OC -- sort of entering entering a person's mind and looking around and seeing. Saying where can I cause trouble and so what better way for IOC do you torture than to say you can't be in the same home with her -- The doctor -- project to -- I -- the prize and all of the things she's had to give up her family been for months and she's been home. She lives with her grandmother nearly an hour away. And all of that swimming she -- -- time in the pool. She's been forced to give that to. He can go anything. -- the student. -- -- Food and runs through that in turn. So many parents 86 machine. It's overwhelming it was really didn't apparently encompasses. Everything in life and how -- didn't -- -- it could grow. To where it's where he's now. The treatment we are allowed to witness it rarely shared on camera. What's cold exposure and response prevention therapies. -- must expose yourself to work appears to desensitize yourself getting closer to her mother one inch at a time -- -- The last week that it and. Richard can talk she wanted to -- on the couch. He doesn't want her mother didn't help either. Okay now your mom -- -- Internet -- -- costs for Bridget he's been in of itself is remarkable progress. During the last visit for mother couldn't even sit on the couch at all. Check of the room much like. Smaragdis -- something BL OC gave me she believes more here -- -- actually as. And what we learn numbers nearly yearlong journey is that project is hardly alone in her fight against OCD. But could of course it was just eight years old when his mother took this video of him. Well I don't remember get the phone and I don't remember at least get them. Iraq was obsession revolves around the fear of getting sick. The fear about what could happen when he leaves for school. -- -- And don't remember. What I can't run I don't remember exactly what it. -- The fear is relentless in hand yeah. And I -- Shakes his mother to repeat yourself to keep reassuring him that everything will be okay but even the most loving -- -- can -- Q. What I said I don't know what I. Why we do that this video was taken just weeks before his diagnosis. Buckled as -- CD to. His fear of what if consumes him. His parents told us it started it was just. Fine. I'll never forget going to carnival he was on a merry go -- -- in. Think you're supposed to have fun -- -- this kid crying and. And even now with times when he asked the questions it's really hard to have the patience -- -- you know huge flying. And so I get over it is not an off for a headache and you know what you have to pay you. Tiny I don't know what you're saying I don't remember what I said about the -- you'll have great day why do you do this isn't a cut and cynical. -- What he's like your -- this is like you -- like the school board. Coming from San Jose but I can't live like this -- living god. That the word of what we did no better. -- -- -- Parents torment watching their little boy struggled to get past his anxiety all of this -- and on this morning buckled as he did not for the school yet. Ago about. We may -- McCann built two for -- to struggle just to get out of bed for school. Just fifteen when she was diagnosed her obsession is being clean. Scrubbing herself into her skin is raw. And just one round of this. He's never. So frustrated some warnings. She punches holes in the wall. All of this Washington -- still has to take a shower. And -- -- her. -- some of these eastern -- decider in team in the -- line is he takes several hours even on a good thing. Just to get out of the house. Washing hands -- infected person. Many innocent sheriff from fourteen years old has ever -- me. And finally we met Michelle can't even get to school it's hard for her even -- in public would -- be able to open the door. -- -- -- Melinda when we combat what -- whom is Michelle still afraid. How could a department store settle for panic attacks and nightmares. And why does that lead to thoughts of giving them. The literary and -- and living in. -- fifteen year old Virginia sits in the waiting room two seats apart from the mother. -- obsessive compulsive disorder her fear of contamination. Prevents her from sitting any closer. The last time they were here they worked the entire time and simply sitting on the same couch. Karen has not been able to hug her daughter for months now and it is Bridget -- in the driver seat. It is -- painstaking process every time it's taken seven full therapy sessions just to get this -- on the couch. Her mother's slowly moving her body closer. All is going well. The -- your money reaches for congress to keep their past. Bridget is a -- getting close to that person who contaminate -- Okay -- And now deciding how shall leave the office with her mother is a fight against fear. -- -- -- -- -- -- -- -- -- -- -- All of this is irrational and Bridget like so many children we -- CD. Knows that but she still afraid that her mother and the rest of her family home is contaminated. And Bridget refuses to go there. Her mother is about to -- for nearly an hour away -- -- grandmothers. Project has been living for four months. Often and put them on top and I -- Friday's. For Bridget everything's complicated even the simplest of things but getting into the car where she could -- -- when she's in the -- -- I can't be. -- -- -- We'll. Have inside another -- another mother and daughter in their own relentless fight against -- CD. What -- you trying to tell -- Fourteen year old Michelle LeClair who hasn't been able to step inside her school for four months now. Her mother Diane LeClair had to quit her job as a teacher it to work full time helping Michelle point -- CD. When she -- the school she would cry for Callahan. -- -- -- -- -- school but I couldn't touch her -- -- CD also involves contamination. Which or fear is different. Her -- wine needs to kids at school she's afraid afraid their dirty. She can go to school or anywhere in public where she is seen the other student. We had to go right hours away just. Get -- a -- parents. Get cleaning supplies because everything around here please contain me all the stores -- because his kids from score and then. It is a crippling fear that has left her isolated. At home. For laundering has begun separately from the rest of the family and one laundry cycles often isn't enough to convince Michelle her clothes are clean. Even -- Washington after the war. She -- -- consistently at home blistering hot water at one point her parents couldn't even get her out of the shower not even when there was a brand new puppy in the home. We're gonna go KB toys take into the storage and so excited -- -- -- after an hour Charlotte wouldn't need to leave if you. -- -- She just saddened to -- rocked -- -- Who CD took -- for money. This is so -- -- democracy with children who -- who CD Michelle plunged into depression. I -- to -- because I couldn't touch anything. Handling can't really -- anything can do anything. -- -- -- -- Whether Bryant cleaned and living. Four different portrait the little girl who was want to straight A student a dancer and book dressing up. Child who once proudly displayed her smile. Your school situation -- -- would we've been -- with her she'd already begun therapy with doctor -- And she and her mother are taking the next step on the Rome actually practicing going to school. The holes are empty. They're headed to their first off the law. When it's convenient and and so it has the -- thing and then. -- the door -- you know. The doctor has told Michelle to touch what she's afraid of what's dirty. And -- to touch yourself prove that there's nothing W freedom. The -- told her to keep track of her anxiety on a scale of one to ten. Oakland. Won't. Thanks for long -- you know touching. -- only taken eight cents. -- Early containment council on Clinton. And say thank. Right. With the locker room no Concord the next battleground gym class it's been five months since she stepped foot inside the jets. You have -- -- metal roof and a million people came here. You know hidden tax that. Isn't feeling. -- it can -- like. Coming. Into -- really. Going doing live. -- full time coach her mother takes -- look -- And very friendly didn't detect the walls he's saddened but then she touched -- -- A proud mother and her daughter leave school. After their own sort of Jim practice. Well back -- that therapist's office. -- -- is still far from over. -- is about to take a huge step to. It's been eight sessions QB eight hours of intense therapy with doctor way she still has not love her mother to -- -- It's been months since mother and daughter and -- Sorry that's pretty good. Bridget and her mother grasp the small want to between him. So. Lots of things that unions. -- Find -- center. Sure -- -- students to make doing. Just stay with it. BC is the first time Bridget has touched her mother. In four months. -- -- -- -- -- -- -- -- There is that it's really. She looks. It's very difficult for parents to -- in -- monopoly that they've done something wrong -- kid has all these fears and. And strange and bizarre few years -- and I do wrong. 12 fears -- the doctor pushes bridge that hold us hand again and this. This. They're pretty good here. But as we were about to learn Bridget OCD fight is far from over really caused this. And we wonder what's really going on here. So for folks -- just in the child's head you found it literally isn't the breakthrough science that just might help set these children free. When we come back how often do you do this the -- took the stole more than once. And what these brand new brain scans reveal anyone's ever thought they might have OCDs. Next. After four months at home paralyzed by fear or afraid other students -- -- contaminated. -- -- tries to go back to school one class at a time. Science classes first. Dorm room you three. Felt like old tonight get back perform scenes like. I can do it she's crossed the first big -- she's there in collapse. That right away within minutes of the first period we noticed Michelle is already anxious about something. Asking about the eighth grade bomb an overnight trip to Hershey park -- it makes a trip that still two months away. She can't imagine in the overnight we will wait for home and she's just trying to repeat his movement -- -- This chaotic capital. Only here because their kids -- -- where have you won't. It is not just your friends asking questions and even the principal seemed uncertain. About just how to handle Michelle and her first day back. Put -- I'm here to kind of -- behind the eyes and she didn't blink and she high five me and I knew the right track. Michelle has made it back to school but next comes the -- -- this has nothing to do with schoolwork this is the continuing fight against her OCD. After school she goes to -- the one department store she fears most. -- -- -- Not because of the store itself but because of the other students -- scene there -- going to be able to pull into the parking lot. Can you stick your hand out -- Linda. What's happening. -- -- -- -- -- -- -- her -- is irrational. But that is OCD. -- -- -- -- Still -- here on -- -- out of the Clark. In the reaches down to touch the patent. She -- touches your daughter to -- for nothing bad would happen. Now the hard part actually walking toward the store. The entrance and Michelle hasn't walked through. Over four months. -- -- -- What about the people out there who might say you know were were enabling these children and a little tough love. Would would probably be better just push him into the department store clerk think about when you are afraid. Of anything if someone tries to push you against your will. Part of and you feel ready to your tendencies to dig your heels to say you know to just pull back. They want to get better there's nobody more motivated than they are to stop this thing from controlling their lives. Do I want -- of course just. Online the idea is bad ones you face your fear and -- basically over and over and over and over a period of time you become less sensitive to. -- -- -- -- Yeah. After nearly making that front door of the store. Hug from her mother even -- Michelle was unable to go inside they still consider this a -- milestone. Before they head home for the day. Well -- -- that their purpose office Bridget is still twice to get home for her it's been six months -- a week for her family and. Home. And Bridget is about to face her biggest fear of all -- to be contaminated by her own father -- six months it's been six months. Since -- even spoken. -- fifteen these missed half of that year. -- -- Her father walks in. And because he works undercover -- -- and the family has asked us that we not to his feet. Make eye contact with -- own father. -- -- -- -- I'd like you try. To -- -- yourself. -- in the room for 35 minutes project still trying to calm down she still can't even look in the direction -- her own father. And in the small steps begin Bridget Muster the courage. To look at her father's shoes and Brandon -- Anything. Because this is where. The doctor asks Bridget to look beyond the -- beyond the hands directly at her father a full hour has gone by. Then she never looks do you -- -- yeah. Her father. Leaves the room. We wondered -- she ever breakthrough. Can she ever go home. We'll be OCT win. Doctor David Rosenberg is convinced bridges and other children like Kirk can conquer it. His team at the children's hospital of Michigan is on the front -- to -- against -- CD. In a ground breaking study they're now looking closely at the animal rights of children who have OCD they can actually see -- The brain's anatomy it's make up the child's genetics. Actually revealed the disorder. Chemical it's physiological and we can see -- iron -- The doctors here say they made a major discovery and big deal with the brain chemicals -- is critically involved in ocean dean -- the brains light switch. And there's either too much or too little bit children who have the disease which means -- -- which is broke. And it turned the part of the brain it gives most of us the all clear when we were -- Ever gets. Message they never. Get the all clear signal they have to worry obsessively over and over again because the brain's arousal center. She's just giving him the message that you have to check -- and over. Many of us just stores would be -- the house with a still sometimes two or three times constantly asking ourselves questions about it looks like. -- did with his mother I don't remember -- get a -- and eventually our -- give us the message that it's -- to move on. With children who OCD. Instead of saying relax this and worry more alarmed danger and for -- meeting we might get an alarm but then once we check the alarm goes away. Exactly right it tells us -- there's nothing to worry about that never happens in a child with obsessive compulsive. This. And once doctors could pinpoint what's going -- the medication can help reset that chemical imbalance. Anti depression or anti anxiety medication is most often used. Depending on the child. That's significant. -- huge. Huge because the doctor says you don't know we -- this typically takes 72 weak years for parents to find the -- kind of help to do children. Many parents don't deal with their child. The suffering from and now they say this combination of the right medicine and that exposure therapy we've now been witnessing for months and get help children keep there were recent days. In these doctors aren't the only ones trying to get the word out. My name's I wasn't -- and I have obsessive compulsive disorder. Remember Elizabeth she was a teenager who once punched holes in her wall she got that health therapy and medicine. And since that home video three years ago she's now gone to college and she is now the national spokesperson for the obsessive compulsive foundation. How long did it take. You -- rain this morning. I'd say 3040 minutes went typical girl talent is take a typical -- they're adding that's a huge -- -- remembered taking. Five to six hours hours. And if she could do it we wondered what about -- My parents parents told us they couldn't get him on -- merry go round without watching duke boy dissolve his worries about what could happen about getting sick. Just weeks ago we met -- again at New York's Central Park. He is now an anti depressant medication that medicine and therapy he's working. On this particular morning he did struggle to get out of the house he got here. Under that merry go round. -- -- He boasts of his baseball team's record. But his parents know the biggest victory was just getting here all of those mornings they couldn't get him -- the front door. Thinking of -- -- make a great team the -- distance of the poor. They can walk to school. Even for -- thinking -- speaking. -- putting -- mean -- and help Rocco understand pain I have OCD. In this town than in dealing. What our journey with the children is far from over. When we come back to young women still facing their biggest hurdles. -- fall away from home. And a simple ability to even go home safe and may do it without their OCD taking over. Bridget has now reached her final hurdle whose own father. Last time she couldn't even look at him. Yeah. -- -- -- To date she gets closer much closer. To doctor -- who is touching her father. Go ahead of. In vanity project touches her father Purcell the first time in six months. He's got to make her laugh cry her left the -- Controlled. These are less steps before Richard decides she can finally trying to -- I can't -- in the senate candidate the next session in predicts it's between her parents on the couch she's about to move toward father. And finally. And breaks. This was undoubtedly her biggest breakthrough yet. She tries to get home. While for Michelle the biggest challenges that -- away from home at eight grape -- in overnight trip. Some of those same students she once fear that this -- Shell's biggest night of the school year the prom. Cameron -- -- doing getting ready for it. How's it gonna get credit problems and so this is the fancy dress loud -- angry. She's proud of her dress proud of being here at a friend's ratings they're proud of Michelle Monaghan she has kept OCD a secret until now. -- -- -- Pet like this live this way she always -- -- If Clinton had in fact if you don't contact. -- -- people. But that's your friends get ready in that room to show he's fighting -- CD on the inside. You don't do school activities and. It's. The end you know mostly -- and then that's not money. Room. Not the only thing only. You. It's it's fifty. A lot of people might think well that's just being a little homesick but everybody gets that. He had. But I think for me because -- and -- family. For just -- -- straight it's hard for -- And you're feeling all. Right. Do you feel badly because you left them. But I know -- up my home and am looking. So you doing this in part for them. -- -- -- -- -- As -- rules assemble in the hallway as they ready for the ball -- Michelle shares the anxiety that he's creeping back. I kind of had to -- -- -- she has already tested the bed like sitting up. Just to prove yourself to the dead were strangers had slept. -- crude dirty. Just like she tested that Jim Walker long before and that -- -- the -- or what but this time she was testing yourself without the -- for coach. You did it on your own that your friends were in the room. Thinking they even knew that you were trying to -- Her friends are waiting that bomb about to start it just outside just out of sight mom -- as well it just -- I don't want anybody to see me I don't want her -- But I need to be close enough that if she does have a panic attack course you can't do it bad that I can be able to do. There. When we come back we search for Michelle -- -- -- through. What would we find. Wells -- British house where she is -- home. We were not expecting what happened next -- -- After spending nearly half year -- away from her own family. Bridget he's he's finally back -- -- it was a trademark smile she so often flashed. Tonight -- products and I and -- coming back home side get this thing lights. False -- cheering -- deal with the same family that she was once who terrified. Terrified that they would contaminate. To take -- to a room. I give us a little more on -- -- here. -- -- -- -- -- -- On I can't exceeds a blanket because. I know who has just like this before so I think with a bathroom which is actually quite he thought it had backed. She tells us sleeping with a bathroom and the floor still better than moving away from home. And project every day remembers doctor -- were acts. Get a face if if it's flying into the dark. But flying into the darkness still isn't as easy as it sounds she -- through the house to the doorway again. She -- She tells us she can't -- when. You feel like it's -- back. -- -- I'm very good morning -- and making it look like going to get that's how my mom does -- did you -- an island and -- bands like athletics. Imam did you notice. On its -- yeah. And it's usually comes and hurt you know me five minutes and that it. Now -- admits she can't make herself go into the -- at all. It is a major step back. -- -- Pressure from other parents who might say why -- -- meters and. When she's not ready and that's a horrible -- -- to see someone you know go through. We noticed her brother sitting inside the -- he's nineteen and he knows his sister is still tormented by fear I'm curious what goes through your mind mr. watching. -- -- -- Through this we know that this is her fault -- I think that there's probably a point when she thought that read. Read we're blaming her for -- and that's definitely not the case he told us he's proud to -- sister and out of his mother helped her to get here. Do you feel sorry for your -- given what she's been through. Full I always knew it if if -- -- -- -- -- sit at a -- hosted the nicest person in the world and you know statement went on that in itself pretty difficult process for her and I think she's. Good I'm glad she's -- -- -- They are all taking it one -- time. Welcome -- that time has -- rise -- -- she still fears. Please take a week for all of those kids looking for the fourteen year old who wants couldn't get out of -- -- helps shell we're in for hours. -- teenager who couldn't step inside her own school terrified of the locker room. The fourteen year old who couldn't go shopping. Now after all of that on the other side of the dance -- We found it. Show dancing with the friends. And just outside her mother out of sight. Wondering if her daughter out of the woods. She's tearing up the dance floor now really on the dance floor off -- too -- for her. Big -- -- -- And so its -- Are you proud. It was still one final tests -- Moment even we thought unimaginable -- this journey began. Bridget is about to get into the front seat of the car with her mother. Something she could do just a few months ago but we were they going. To the school were to assume that the water so loved as a little girl. And the mother who told -- she -- 181000. Miles driving back and forth to grandma's house for project was living. He's a great with a shorter trips frequently have her daughter -- breaking the front seat next door. Letting us Richard told us it is hard to believe she's here. We initially the butterfly Austin is a butterfly half an -- -- yeah we were there today you told doctor away. That you were going through this therapies that it's -- again. That would be better. We watch. -- butterfly this comes -- life. Never gave up. -- -- -- Every person that's ever been willing to share this story about whether. We'll talk to a friend about enterprise national -- about and -- -- -- this thing. Day by day person like -- true believer. There is hope and OTB look back -- That's the biggest things in OC -- pulling -- if you fight. My nightmares. -- -- For all of these children it took months of excruciating therapy for them to break away from their OCB. Tonight we salute their bravery and their willingness to take a -- on the journey. But behind every one of -- success stories -- say there are countless other children waiting for the right kind of help you can find more information at abcnews.com.