We report the results of a J -band survey for photometric variability in a sample of young , low-gravity objects using the New Technology Telescope ( NTT ) and the United Kingdom InfraRed Telescope ( UKIRT ) . Surface gravity is a key parameter in the atmospheric properties of brown dwarfs and this is the first large survey that aims to test the gravity dependence of variability properties . We do a full analysis of the spectral signatures of youth and assess the group membership probability of each target using membership tools from the literature . This results in a 30 object sample of young low-gravity brown dwarfs . Since we are lacking in objects with spectral types later than L9 , we focus our statistical analysis on the L0-L8.5 objects . We find that the variability occurrence rate of L0-L8.5 low-gravity brown dwarfs in this survey is 30 ^ { +16 } _ { -8 } \% . We reanalyse the results of \citet Radigan2014a and find that the field dwarfs with spectral types L0-L8.5 have a variability occurrence rate of 11 ^ { +13 } _ { -4 } \% . \added We determine a probability of 98 \% that the samples are drawn from different distributions . This is the first quantitative indication that the low-gravity objects are more likely to be variable than the field dwarf population . Furthermore , we present follow-up J _ { S } and K _ { S } observations of the young , planetary-mass variable object PSO 318.5–22 over three consecutive nights . We find no evidence of phase shifts between the J _ { S } and K _ { S } bands and find higher J _ { S } amplitudes . We use the J _ { S } lightcurves to measure a rotational period of 8.45 \pm 0.05 ~ { } hr for PSO 318.5–22 .