vertical space between paragraphs and `topsep` in \usepackage{enumitem} cancel each other out

Question

I'm using \setlength{\parskip}{\baselineskip} to insert vertical space between the paragraphs in my document. However this create a conflict with my list environments. To solve that I am using the enumitem package to set the space between the last line before my itemize environment and my first item to =0pt however, the paragraph spacing created with \setlength{\parskip}{\baselineskip} cancel this out. I can get at it by setting topsep to ~ -9pt, but them I loose the spacing between the last item and the next paragraph (MWE is below). I have deliberately chosen noitemsep as I also want less spacing between the individual item, I would like to keep this.

\documentclass{article}

% insert vertical space between paragraphs
\setlength{\parskip}{\baselineskip} 

% Modifies itemized lists with enumitem http://www.ctan.org/pkg/enumitem
\usepackage{enumitem}
 \setlist[itemize]{noitemsep, topsep=0pt} % , topsep=-9pt

 % http://tug.ctan.org/tex-archive/macros/latex/contrib/blindtext/blindtext.pdf
\usepackage{blindtext} 

\begin{document} 

\blindtext

\noindent
This is the things cancel each other out:
% space I would like to get rid of is here!
\begin{itemize}
\item dummy first item
\item insert vertical space between paragraphs
\item \verb|[topsep=0pt]| in \verb| \usepackage{enumitem} |
\item dummy last item
\end{itemize}

\blindtext

\blindtext

\end{document}

Answer 1

Add before={\vspace*{-\baselineskip}} to your itemize options:

\setlist[itemize]{noitemsep, topsep=0pt, before={\vspace*{-\baselineskip}}}

MWE:

\documentclass{article}

% insert vertical space between paragraphs
\setlength{\parskip}{\baselineskip}

% Modifies itemized lists with enumitem http://www.ctan.org/pkg/enumitem
\usepackage{enumitem}
 \setlist[itemize]{noitemsep, topsep=0pt, before={\vspace*{-\baselineskip}}} % , topsep=-9pt

 % http://tug.ctan.org/tex-archive/macros/latex/contrib/blindtext/blindtext.pdf
\usepackage{blindtext}

\begin{document}

\blindtext

\noindent
This is the things cancel each other out:
% space I would like to get rid of is here!
\begin{itemize}
\item dummy first item
\item insert vertical space between paragraphs
\item \verb|[topsep=0pt]| in \verb| \usepackage{enumitem} |
\item dummy last item
\end{itemize}

\blindtext

\blindtext

\end{document} 

Output:

Answer 2

karlkoeller's answer works great for some time, but you should be aware of the following:

Using negative vspace for the environment can have unwanted side effects as in this question happened to me. The manipulation of vspace leads to Latex calculating the wrong vertical size and can lead to the page content overflowing for example the footnote area.

Instead you should manipulate \topsep before (and after, if necessary) the environment, to make it consume less vertical space.