- Email: [email protected]
Reply to Fan and Hart
Psychiatry Research: Neuroimaging 191 (2011) 85
Contents lists available at ScienceDirect
Psychiatry Research: Neuroimaging j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / p s yc h r e s n s
Letter to the Editor Reply to Fan and Hart We thank Fan and Hart (2010) for their comments on our article (Dekker et al., 2010). We agree that using the term ‘brain abnormalities’ could be seen as less appropriate. We twice use this term in the discussion when we state that ‘cannabis naïve schizophrenia patients showed brain abnormalities in the splenium of the corpus callosum, compared to early onset cannabis users’, and later when we state that ‘we identified congruent anatomical and diffusion abnormalities manifesting in the posterior corpus callosum, a brain area adjacent to the PCC, in cannabis naïve schizophrenia patients.’ As Fan and Hart (2010) suggest, the word ‘abnormality’ should only be used when there is a difference from the normal. Therefore, in future articles, we agree that it is better not to use the word ‘abnormalities’, but ‘reduced fractional anisotropy (FA) values’ or ‘reduced white matter density’ when we refer to comparisons within patient groups. However, we do not agree with their argument that the naïve group's fractional anisotropy integrity appears to be within the normal range of healthy male adolescents, with reference to Ashtari et al. (2007). For the current study we used voxel-based morphometry (VBM) methods to discriminate between the FA voxel intensities on a voxel-by-voxel basis (Ashburner and Friston, 2000). We refrained from calculating the mean FA values or extracting a tensor since we were interested in the whole brain response of our study sample. Therefore, our data cannot necessarily be compared with those of Ashtari et al. (2007). Furthermore, voxel-based analysis (VBA) does not permit the generation of ‘normal ranges’ of FA values; it serves as a comparison of numerical values between 0 and 1 without a unit, with a higher FA value implying a higher degree of anisotropic motion of water molecules. Fan and Hart argue that our title ‘Cannabis use and callosal white matter structure and integrity in recent-onset schizophrenia’ would imply that there was an effect of cannabis on the onset of schizophrenia and brain abnormalities in the current participants, while our data did not demonstrate an effect of cannabis use. Indeed, we did not find an effect of cannabis use. However, in our opinion the
0925-4927/$ – see front matter © 2010 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.pscychresns.2010.08.009
title is neutral. The title captures two important topics in our article, namely cannabis and the corpus callosum, and therefore informs the reader—at a single glance—what our article is about. We do hope and think that casual readers who might by chance misinterpret the findings of our study by only reading the title will later be correctly informed about our results and conclusions by reading the abstract. References Ashburner, J., Friston, K.J., 2000. Voxel-based morphometry — the methods. NeuroImage 11, 805–821. Ashtari, M., Cervellione, K.L., Hasan, K.M., Wu, J.H., McIlree, C., Kester, H., Ardekani, B., Roofeh, D., Szeszko, P.R., Kumra, S., 2007. White matter development during late adolescence in healthy males: a cross-sectional diffusion tensor imaging study. NeuroImage 35, 501–510. Dekker, N., Schmitz, N., Peters, B.D., Van Amelsvoort, T.A., Linszen, D.H., De Haan, L., 2010. Cannabis use and callosal white matter structure and integrity in recentonset schizophrenia. Psychiatry Research: Neuroimaging 181, 51–56. Fan, L., Hart, C.L., 2010. Letter to the Editor. A call for more care when investigating the cannabis-psychosis link. Psychiatry Research: Neuroimaging 191 (1) XXX-XXX. [Insert pp. numbers when known - this is PSYN_9680, which immediately precedes PSYN_9684].
Nienke Dekker⁎ Nicole Schmitz Bart D. Peters Therese A. van Amelsvoort Don H. Linszen Lieuwe de Haan Department of Psychiatry, Academic Medical Centre, University of Amsterdam, Meibergdreef 5, 1105 AZ Amsterdam, The Netherlands ⁎Corresponding author. Tel.: +31 20 8913500; fax: +31 20 8913536. E-mail address: [email protected] (N. Dekker).
13 August 2010
Contents lists available at ScienceDirect
Psychiatry Research: Neuroimaging j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / p s yc h r e s n s
Letter to the Editor Reply to Fan and Hart We thank Fan and Hart (2010) for their comments on our article (Dekker et al., 2010). We agree that using the term ‘brain abnormalities’ could be seen as less appropriate. We twice use this term in the discussion when we state that ‘cannabis naïve schizophrenia patients showed brain abnormalities in the splenium of the corpus callosum, compared to early onset cannabis users’, and later when we state that ‘we identified congruent anatomical and diffusion abnormalities manifesting in the posterior corpus callosum, a brain area adjacent to the PCC, in cannabis naïve schizophrenia patients.’ As Fan and Hart (2010) suggest, the word ‘abnormality’ should only be used when there is a difference from the normal. Therefore, in future articles, we agree that it is better not to use the word ‘abnormalities’, but ‘reduced fractional anisotropy (FA) values’ or ‘reduced white matter density’ when we refer to comparisons within patient groups. However, we do not agree with their argument that the naïve group's fractional anisotropy integrity appears to be within the normal range of healthy male adolescents, with reference to Ashtari et al. (2007). For the current study we used voxel-based morphometry (VBM) methods to discriminate between the FA voxel intensities on a voxel-by-voxel basis (Ashburner and Friston, 2000). We refrained from calculating the mean FA values or extracting a tensor since we were interested in the whole brain response of our study sample. Therefore, our data cannot necessarily be compared with those of Ashtari et al. (2007). Furthermore, voxel-based analysis (VBA) does not permit the generation of ‘normal ranges’ of FA values; it serves as a comparison of numerical values between 0 and 1 without a unit, with a higher FA value implying a higher degree of anisotropic motion of water molecules. Fan and Hart argue that our title ‘Cannabis use and callosal white matter structure and integrity in recent-onset schizophrenia’ would imply that there was an effect of cannabis on the onset of schizophrenia and brain abnormalities in the current participants, while our data did not demonstrate an effect of cannabis use. Indeed, we did not find an effect of cannabis use. However, in our opinion the
0925-4927/$ – see front matter © 2010 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.pscychresns.2010.08.009
title is neutral. The title captures two important topics in our article, namely cannabis and the corpus callosum, and therefore informs the reader—at a single glance—what our article is about. We do hope and think that casual readers who might by chance misinterpret the findings of our study by only reading the title will later be correctly informed about our results and conclusions by reading the abstract. References Ashburner, J., Friston, K.J., 2000. Voxel-based morphometry — the methods. NeuroImage 11, 805–821. Ashtari, M., Cervellione, K.L., Hasan, K.M., Wu, J.H., McIlree, C., Kester, H., Ardekani, B., Roofeh, D., Szeszko, P.R., Kumra, S., 2007. White matter development during late adolescence in healthy males: a cross-sectional diffusion tensor imaging study. NeuroImage 35, 501–510. Dekker, N., Schmitz, N., Peters, B.D., Van Amelsvoort, T.A., Linszen, D.H., De Haan, L., 2010. Cannabis use and callosal white matter structure and integrity in recentonset schizophrenia. Psychiatry Research: Neuroimaging 181, 51–56. Fan, L., Hart, C.L., 2010. Letter to the Editor. A call for more care when investigating the cannabis-psychosis link. Psychiatry Research: Neuroimaging 191 (1) XXX-XXX. [Insert pp. numbers when known - this is PSYN_9680, which immediately precedes PSYN_9684].
Nienke Dekker⁎ Nicole Schmitz Bart D. Peters Therese A. van Amelsvoort Don H. Linszen Lieuwe de Haan Department of Psychiatry, Academic Medical Centre, University of Amsterdam, Meibergdreef 5, 1105 AZ Amsterdam, The Netherlands ⁎Corresponding author. Tel.: +31 20 8913500; fax: +31 20 8913536. E-mail address: [email protected] (N. Dekker).
13 August 2010