figure for 2 sample mr paper

fig1a.tex

\documentclass[12pt]{article}
\usepackage{tikz}
\usetikzlibrary{positioning}
\usepackage{times}
\begin{document}
\thispagestyle{empty}
\begin{figure}
\begin{tikzpicture}[every node/.style={minimum height={1.5cm},thick,align=center}]
\node (T) {\textbf{Genetic instruments for GERD} \\ 59 independent SNPs};
\node[below left=6cm and 0.7cm of T] (G) {\textbf{GERD}};
\node[below right=6cm and 0.7cm of T] (I) {\textbf{IPF}};
\draw[->,line width=1pt] (T) -- (G);
\draw[->,line width=1pt] (T) -- (I);
\draw[->,dashed,line width=1pt] (G) -- (I);
\node[text width=7cm] at (-5,-3) 
    {\textbf{Gene-GERD (G-X) estimates} \\ 462753 GERD cases, \textgreater 1 million controls};  
\node[text width=7cm] at (5,-3) 
    {\textbf{Gene-IPF (G-Y) estimates} \\ 4125 IPF cases, 20464 controls};
\node[text width=6cm] at (0,-9) 
    {\textit{Causal effect estimate \\ of \textbf{GERD} on \textbf{IPF} risk}};
\end{tikzpicture}
\end{figure}
\end{document}