How can I change the spacing before theorems with amsthm?

Question

I have a spacing problem. Whenever I include a theorem environment, \begin{theorem}\end{theorem}, the theorem appears very close to the previous line. The spacing is much less than the normal spacing between lines. Do any one have any idea to change this? I don't just ad hoc add \vskip at each theorem environment.

Thank you very much for your help!

EDIT: Here is the style files that I included:

\usepackage[top=2.3cm, bottom=1.8cm, left=3.3cm, right=3.2cm]{geometry}

% -------------------------------------------------
% Common packages.
% -------------------------------------------------

\usepackage{graphicx,subfigure,url,psfrag}

\usepackage{amsmath}

\usepackage{amssymb,amsthm,amscd}

\usepackage{bibcontents}

\usepackage{natbib}

\usepackage[notref,notcite]{showkeys}

\usepackage[noxcolor,usenames]{pstricks}

\usepackage{multirow}

% \setlength{\textwidth}{6in}

\usepackage{parskip}

Answer 1

Put the following code in the preamble:

\makeatletter
\def\thm@space@setup{%
  \thm@preskip=\parskip \thm@postskip=0pt
}
\makeatother

The problem is that amsthm sets \thm@preskip to \topsep, which is zeroed by parskip.