Can I quit my summer internship and still get into grad school?

[chemppl]

I'm currently doing research as part of the Department of Energy's SULI program at one of their national labs. The program is not what I expected, and the experience is very hard on my mental health. I'll be applying for grad schools in the fall, and have a 3.9 GPA and have done research at my undergrad institution, which includes a trip to the ACS national meeting. My research professor told me that I was welcome to continue researching over the summer in my usual lab if I decided to quit. How much less competitive is my grad school application without this program on my resume? 

[pchem2018]

I wouldn't expect that your application would be less competitive if you decided to quit. I am applying for grad schools in the fall this year too, and my research advisor told me not to do an internship, and to instead continue to do research. If you are doing research in a lab you should be fine. Of course, if I was you I wouldn't include this internship on your application if you decide to quit. Of course, that's just my opinion, but it seems that most students at my university who are applying to PhD programs don't do internships, they just research with their advisor.

[ochemist94]

The most important thing is to do keep doing research that you love. Since you can join your usual lab if you quit, I think it's okay to quit. I had a similar GPA and attended ACS meetings as well.  I did not do any internship.  I worked in a lab at my institution for ~4 years and was able to get into top PhD programs in chemistry. Good luck!