Denise Kandel (German: [ˈkandəl]; née Bystryn; born February 27, 1933) is an American medical sociologist and epidemiologist, Professor of Sociomedical Sciences and Psychiatry at Columbia University and Head of the Department of Epidemiology of Substance Abuse at the New York State Psychiatric Institute.

[citation needed] Bystryn was born to Jewish parents who emigrated in the 1920s, before knowing each other, from eastern Poland to France to attend university.

Her mother Sara Wolsky Bystryn (1906–2003) had to abandon her plans to study in Paris for financial reasons and learned making hats and corsets.

[3] The family lived in Colombes near Paris, and Kandel attended a primary school for girls (Ecole des Filles).

Kandel was able to stay as a pupil in the convent Sainte-Jeanne d'Arc of Cahors until spring 1944, when she had to flee even from there and then lived with a family near Toulouse.

Her research in this area found a strong resonance in scientific and political discussions, and the catchphrases "stepping-stone theory" (used since the 1930s) and "gateway hypothesis" (used since the 1980s) were associated with her name, though often misleadingly.