Disclaimer: I do not own Sherlock Holmes, John Watson or 221B Baker Street. Not in the slightest.

Summary: After Sherlock reads an article on the benefits of kissing, he convinces John to take place in a few snogging sessions. . . for science! Lots of medical lingo. There will be five parts in all.

Warnings: Some mild cursing.

Word Count (this part): 1,620

A/N: I won't lie; this chapter is slightly angsty at the beginning. Very different from the other chapters... Just a heads up!

Anyway, it's finally the end! This is the last chapter, my friends. Thank you all for sticking with me through this, and I really hope you enjoy!

A Study in Stress

Sherlock was sitting downstairs watching crap telly when he heard the scream come from John's bedroom.

The detective jumped to his feet and made his way upstairs as quickly as he could. He burst through John's bedroom door, and quickly took in what he saw: John was tossing and turning in his bed, his bed-sheets strewn about, and sweat gleaning all over his body.

Sherlock made his way over to the bed and slowly reached out a hand, grabbing the still sleeping John's shoulder and shaking it slightly. "John," Sherlock said quietly, but the doctor didn't stir. "John!"

John jerked awake, his arms rising as though he was trying to shield himself from being hit.

Sherlock yanked back his hand from John's shoulder and stared down at his flatmate. "It's just me, John. It's all right. . ." He reached his hand back out and placed it on one of John's raised arms, slowly easing pressure onto it until John relaxed and let it fall down to his chest.

Once his arms were no longer shielding his face, Sherlock noticed the distinctive glisten of tears on his cheeks. He moved his hand up to John's face and slowly wiped the moisture from them with his thumb. John closed his eyes, trying hard to calm himself, but his breathing was still rapid from the nightmare he had just been roused from.

"You're fine, John," Sherlock soothed. "You're at our flat on Baker Street, not back in Afghanistan. There are no casualties. . . " Sherlock ran his hand through John's short hair. "It's just us here, John. . . It was only a dream."

John slowly opened his eyes as his breathing became less laboured, and he immediately directed his attention to Sherlock. The doctor reached out his right hand and wrapped it around the back of his flatmate's neck.

"Oxytocin and cortisol," was all John said before he pulled Sherlock down for a kiss.

As Sherlock kissed back, a stream of thoughts shot through his mind.

'Oxytocin is the chemical that reduces one's anxiety and calms him or her down. Cortisol is the stress hormone. It lowers as oxytocin is secreted into the bloodstream, thus reducing stress even further. Kissing releases oxytocin, thus providing John's reason for kissing me; he needs to calm down.'

John pulled back slightly and muttered, "Stop thinking, Sherlock," against his lips.

Sherlock obliged, bringing himself from the leaning position he had been in to a better suited kneeling position with his knees on the bed next to John. He moved his hand from John's hair to his neck, cupping it gently as he pulled him a bit closer. The kiss was slow and easy, neither attempting to push it past the leisurely pace.

Sherlock's mind was pleasantly blank, the buzz he was getting from the kiss muting any and all background noise that was usually present. The last four times they had kissed, his mind had this exact same response; the only thoughts that made their way through his brain were ones of John and how incredibly soft and lovely his lips felt against his.

The kisses gradually slowed until they stopped altogether. Sherlock brushed his lips against John's once more before he pulled back and rested his forehead against the doctor's, his eyes still lightly closed.

He massaged slow circles on John's neck with his thumb as they sat there, neither man moving for a few minutes as they simply enjoyed the comfort and the calmness they both felt from the kiss.

Sherlock pulled back and slowly opened his eyes, watching as John's eyes re-opened and focused on him. John smiled up at him and brushed his thumb over his neck.

"Thank you," John said. "I. . . I really needed that."

Sherlock grinned down at him in response. "I'm glad I could help," he said, "seeing as it was for science and all."

The smile on John's face faltered for a split second before he could stop it. Unfortunately for John, Sherlock's observational skills didn't fail him.

"What?" Sherlock asked, his head quirked slightly to the side with a questioning expression on his face.

John removed his hand from the side of Sherlock's neck and pushed slightly on his chest so he could sit up. Sherlock sat back, slight confusion still evident on his face as John moved to a sitting position.

"I uh. . . I need to tell you something." John cleared his throat as he felt his cheeks begin to redden. "I didn't just. . . I want to tell you that I uhh. . ." He faltered once more, not entirely sure how he was going to phrase what he was going to say. "The kiss wasn't just for. . . Um. . . It wasn't just for science, Sherlock."

Sherlock's face went from one of mild confusion to one of complete comprehension.

John kept talking. "I did need to calm down. The nightmare was so realistic, and it just. . . you were being tortured to death, and I couldn't do anything to stop it." Sherlock simply stared at John as he continued. "So when I woke up and you were here, and you were all right, and I was at home with you, I. . . I just realized how desperately I need you in my life. And I know you probably think I'm some patheti-"

John was cut off when Sherlock swiftly leaned forward and kissed him. It only lasted a second, but it was long enough to shut John up, just as Sherlock needed.

"It's fine, John," Sherlock said, his mouth still hovering close to John's. "It's all fine."

A grin broke out across John's face, and he quickly removed the small space between their lips once more.

Sherlock placed his hand back on John's neck, pulling him close. The pleasant silence he was usually greeted with whenever he kissed John was replaced with a semi-guilty thought.

'You have to tell him. He told you his true motive, so he has the right to know yours.'

Sherlock pulled away from the kiss and leaned back so he was a foot or so away from his flatmate. "John, I have a confession to make as well. . ."

The doctor's eyes widened at Sherlock's tone, and he mentally reprimanded himself for telling him the real reason he kissed him. Nonetheless, he nodded, urging Sherlock to continue.

"I haven't been entirely truthful with you, John." He paused for a moment, looking away from his flatmate. "Those experiments I have had you partake in these past few weeks. . . Um. . . They weren't exactly real."

John's jaw dropped, his eyes wide as he stared at Sherlock in shock.

Sherlock continued, "The first one was real, of course, but the others I. . . I made them up. I created some realistic-sounding experiments, hoping they would make enough sense that I could persuade you to let me kiss you again." He slowly brought his gaze back to John, who was still openly gaping at him. "I would understand if you are angry with me for misleading you, but I had to do it. I just had to know. You wouldn't get out of my head, and it was interfering with my work."

John shook his head in disbelief. "I can't believe you!" He gasped. For a moment, he tried to appear angry, but he couldn't keep up the facade, and he broke down into laughter.

To say Sherlock looked confused was an understatement.

"How could this possibly be humorous to you?" Sherlock asked.

John attempted to hold himself together as he said, "I just. . . We are both so pathetic." He laughed again. "You're telling me that we could have been doing this the whole goddamn time?"

John's laughter started breaking down Sherlock's walls, and he began to chuckle as well. "It seems as though we were both having some internal conflicts we were trying to resolve. . . I could say that we have come to some conclusions, have we not, John?"

John wrapped his hand around Sherlock's neck, leaning back until he was lying down with the detective hovering over him once again.

John grinned impishly up at him.

"You know, Sherlock. . . " John said, pulling him closer until their lips were less than a hair's breadth apart. "For an idiot, you're pretty damn smart."