i am doing logit regression with workhours and workhours-square as independent variable and depression as dependent variable with several control variables such as age, educ (dummy), marital status, gender, tenure, working benefit, work stress and per capita expenditure as the proxy of household income. So i have one variable with quadratic form in this regression.

I am a bit confused because the peak point of workhours with or without control variable is different. The peak point of workhours is 35 hours when i regress without control variables. However, the peak point of workhours becomes 64 hours if i regress with control variables. Of course the peak point of 64 hours is not consistent with many literature i've ever read.

The command that i input on stata is:

logit depress workhours workhoursq chronic age elementary middle highschool highereduc single female stress tenure reward pce_pctilei2 pce_pctilei3 pce_pctilei4

is the regression model inconsistent or bias? what should i do to fix my model so the peak point of my regression becomes not really that different?