AN: This was inspired by personal experience. Some people attribute Sherlock's hyperactivity to ADHD; but it fails to explain some of his behavior. Other's attribute it to Asperger's, which seems to fit, but we will give that the benefit of the doubt and, for this story, assume he has anxiety. Now the reason I chose anxiety is because he notices everything. Now, contrary to common belief, anxiety really is an overstimulation of senses that trigger panic attacks; panic attacks have never defined anxiety and never will; they are simply a side effect of anxiety. Now you may ask: Why does this have to do with Sherlock not eating? Well, whenever I forget my anxiety medicine at night I can't focus on anything; I have to focus on everything or dedicate myself to one thing. Also, I never can eat much because I feel dizzy and like I am going to throw up when I have food in my stomach; this is attributed to the overstimulation of senses. That being said, I am not a doctor or a psychiatrist; I merely have an interest in psychology and want to become a veterinary neurologist; but am basing off experience, so please do not judge off accuracy.

Sherlock glared at the food John had given him with disgust, the mere thought of its flavor making him nauseous. He looked back at John.
"No," he stated flatly, carefully monitoring his facial expression so it would not show any inclination of the nausea that was slowly rising in his stomach.
"Sherlock," John pleaded, "I know it's a case, but it's been nearly two weeks since you last ate. You need food."
"No," Sherlock said, resolutely staring into his microscope to not only state the argument was over, but also to provide a distraction from the smell of Chinese takeout.
"Sherlock..." John warned.
"No," Sherlock immediately interrupted, his already ivory skin turning paler by the moment.
There was a moment of silence, with John staring at Sherlock with his arms crossed and a hard look on his face, and Sherlock staring into into his microscope lens to try to control his rising sense of panic.
Eventually Sherlock spoke, so softly that John could hardly believe it had come from a man that could be so intimidating.
"Please. Throw it away John, I can't control it any more."
John looked up, astonished to find Sherlock's face was deathly pale and had taken on a greenish tint.
"Sherlock, what's wrong?" John asked tentatively.
No response.
"Sherlock?" John asked again, seriously concerned for his friend's safety.
"Just get it away," Sherlock whispered.
At this point John was too confused and concerned that Sherlock would be practically begging for help to argue.
So he put the untouched food in the dumpster outside and came back.
To his relief, some of the color had come back into Sherlock's cheeks, but he was breathing heavily and looked scared.
"Sherlock?" John asked softly. "You okay mate?"
Sherlock took in a giant gulp of air.
"Don't," he finally managed to gasp out. "Don't leave me."
John wrinkled his brow in confusion. "Why would I leave you?"
"Everyone else did," Sherlock whimpered, sounding like he might burst into tears.
"Sherlock," John commanded, " Look at me."
Slowly Sherlock's tricolored eyes raised to meet John's steady gaze. John had never seen him look so frightened.
"I will never leave you." John said solemnly. "Do you understand?" Sherlock nodded hesitantly.
"Good," John said, giving an encouraging smile. "Now tell me what's wrong."
Sherlock lowered his head and muttered something unintelligible.
"What was that?" John asked.
"Anxiety," Sherlock whispered a little louder.
John did his best to hide his astonishment.
"And?" John encouraged.
Sherlock took several deep breaths before answering.
"I was diagnosed in sixth grade," Sherlock began slowly. He paused. "My parents were angry that one of their perfect children should be labeled as... mentally incompetent." He cringed at the sound of the words. "So they refused treatment." Sherlock took a moment to collect his thoughts. "I learned that by focusing on work I could prevent my brain from going into overdrive." He gulped. "I figured high-functioning sociopath was better to... explain. Plus," here he grimaced, "I was beaten every time I even mentioned the... correct... name of my mental disorder." Sherlock looked at John with a look of worry on his face.
John stared in awe at his friend for a moment as realization slowly set in.
"So... you don't eat because it unfocuses you."
"Yes," Sherlock confirmed with a brisk nod of his head.
"And... eating nauseates you for the same reason."
"Yes," Sherlock nodded again.
"Oh my gosh, I'm so sorry," John said and pulled Sherlock into a hug.
Sherlock tensed in surprise.
All his life anyone he had confided in had shied away... Or worse, abused him.
But John, Sherlock realized... John was different. John cared. And he wouldn't ever leave.
A genuine smile spread over Sherlock's face.
"Thank you," he whispered.

AN: And that's that! I might elaborate if people would like to hear more of this. Just let me know!

Also, if there is anyone out there struggling with anxiety or depression, know this: You are not alone. The greatest mistake you can make in this struggle is to think you are alone. Don't be afraid to tell you friends; if they can't accept you for that, they are not true. I have struggled with both since sixth grade, and the greatest mistake I made was not letting my friends know from the start.

Finally, I did not write this to justify my symptoms or justify eating disorders. All characters belong to the BBC or Sir Arthur Conan Doyle. I obviously do not own them.