\begin{tikzpicture}
	\begin{pgfonlayer}{nodelayer}
		\node [style=Red Box] (0) at (4, -1.5) {Will Terminate?};
		\node [style=Red Box] (1) at (-4.25, -1.5) {Market Measures};
		\node [style=emptyBox] (4) at (-6, -7.5) {Unobserved};
		\node [style=purple box] (5) at (0, 2) {Enrollment};
		\node [style=Red Box] (8) at (-5.75, -6) {Relationships of interest};
		\node [style=emptyBox] (9) at (12.25, 7.5) {Fundamental Efficacy/Safety};
		\node [style=emptyBox] (10) at (0, 9.25) {Previously Observed Efficacy/Safety};
		\node [style=emptyBox] (12) at (12.25, 0) {Currently Observed Efficacy/Safety};
		\node [style=Gray Box] (13) at (7, -6) {Observed, adjustment set 1};
		\node [style=GreyBoxDotted] (14) at (7, -7.25) {Observed, adjustment set 2};
		\node [style=GreyBoxDotted] (15) at (-4, 4.25) {Planned Enrollment};
		\node [style=GreyBoxDotted] (16) at (4.5, 4.5) {Anticipated Enrollment};
		\node [style=GreyBoxDotted] (17) at (7.5, 3) {Measured Enrollment};
		\node [style=Gray Box] (18) at (-6.5, 1.5) {Population};
		\node [style=GreyBoxDotted] (19) at (5.75, 1.5) {Current Status};
		\node [style=Gray Box] (20) at (0, 7.5) {Decision to procced with Phase III};
		\node [style=Gray Box] (21) at (0, -3.5) {Condition};
		\node [style=Gray Box] (22) at (14.5, -4.25) {Elapsed Duration};
		\node [style=purple box] (23) at (7, -8.5) {Partially observed};
	\end{pgfonlayer}
	\begin{pgfonlayer}{edgelayer}
		\draw [style=lightredarrow] (1) to (0);
		\draw [style=lightredarrow] (1) to (5);
		\draw [style=lightredarrow] (5) to (0);
		\draw [style=RightArrow] (15) to (5);
		\draw [style=RightArrow] (5) to (16);
		\draw [style=RightArrow] (5) to (17);
		\draw [style=RightArrow] (5) to (19);
		\draw [style=RightArrow] (18) to (5);
		\draw [style=RightArrow] (18) to (1);
		\draw [style=RightArrow] (9) to (10);
		\draw [style=RightArrow] (10) to (20);
		\draw [style=RightArrow] (9) to (12);
		\draw [style=RightArrow] (12) to (0);
		\draw [style=Light Arrow] (21) to (1);
		\draw [style=Light Arrow, in=-75, out=105] (21) to (15);
		\draw [style=Light Arrow] (21) to (0);
		\draw [style=Light Arrow, in=-120, out=165, looseness=2.00] (21) to (18);
		\draw [style=Light Arrow, in=180, out=180, looseness=2.75] (21) to (20);
		\draw [style=Light Arrow, bend right=60, looseness=1.75] (21) to (9);
		\draw [style=Light Arrow] (21) to (5);
		\draw [style=lightredarrow, in=135, out=45, loop] (8) to ();
		\draw [style=RightArrow, in=-180, out=165, looseness=2.00] (1) to (20);
		\draw [style=RightArrow, in=120, out=180, looseness=1.25] (10) to (15);
		\draw [style=RightArrow] (20) to (5);
		\draw [style=RightArrow] (18) to (15);
		\draw [style=RightArrow] (22) to (0);
		\draw [style=RightArrow] (22) to (5);
	\end{pgfonlayer}
\end{tikzpicture}
